Extreme ultraviolet light source device and control method for extreme ultraviolet light source device

ABSTRACT

A guide laser beam that has an optical axis and a beam diameter substantially equivalent to those of a driver pulsed laser beam is introduced into an amplification system that amplifies a laser beam that is output from a driver laser oscillator. The guide laser beam is output from a laser device as a continuous light, and is introduced into a light path of the driver pulsed laser beam via a guide laser beam introduction mirror. A sensor detects an angle (a direction) of a laser beam and a variation of a curvature of a wave front. A wave front correction controller outputs a signal to a wave front correction part based on a measured result of a sensor. The wave front correction part corrects a wave front of a laser beam to be a predetermined wave front according to an instruction from the wave front correction controller.

This application is a Continuation of U.S. patent application Ser. No.13/545,786 filed on Jul. 10, 2012 which is a Continuation of U.S. patentapplication Ser. No. 12/612,861, filed on Nov. 5, 2009 now U.S. Pat. No.8,242,472, claiming priority of Japanese Patent Application No.2008-285911, filed on Nov. 6, 2008, and Japanese Patent Application No.2009-251632, filed on Nov. 2, 2009, the entire contents of each of whichare hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to an extreme ultraviolet light sourcedevice and a control method for an extreme ultraviolet light sourcedevice.

BACKGROUND ART

A semiconductor chip may be created, for example, by a reductionprojection of a mask on which a circuit pattern has been drawn onto awafer having a resist applied thereon and by repeatedly performingprocessing such as an etching and a thin film formation. The progressivereduction of the scale of semiconductor processing demands the use ofradiation of a further short wavelength.

Thus, a research is being made on a semiconductor exposure techniquewhich uses a radiation of an extremely short wavelength of 13.5 nm or soand a reduction optics system. This type of technique is termed an EUVL(Extreme Ultra Violet Lithography). Hereafter, an extreme ultravioletlight will be abbreviated as “EUV light”.

Three types of EUV light sources are known: an LPP (Laser ProducedPlasma: plasma produced by a laser) type light source, a DPP (DischargeProduced Plasma) type light source, and an SR (Synchrotron Radiation)type light source.

The LPP type light source is a light source which generates a plasma byirradiating a target material with a laser beam, and employs an EUVlight that is emitted from this plasma. The DPP type light source is alight source which employs a plasma that is generated by an electricaldischarge. The SR type light source is a light source which uses anorbital radiation. Of those three types of light sources, the LPP typelight source is more likely to obtain an EUV light of a higher outputpower as compared to the other two types because the LPP type lightsource can provide an increased plasma density and can ensure a largersolid angle over which the light is collected.

A laser light source device that is configured based on the MOPA (masteroscillator power amplifier) system has been proposed in order to obtaina driver pulsed laser beam of a high output power with a high repetitionrate (see Patent Citation 1 and Patent Citation 2).

Moreover, a technique that uses a deformable mirror in which a variablecontrol of a surface shape can be carried out without any inhibition toa certain extent and that arranges a wave front of a laser beam is known(see Patent Citation 3).

CITATION LIST Patent Literature

[Patent Citation 1]

-   Japanese Patent Application Laid-Open Publication No. 2006-128157    [Patent Citation 2]-   Japanese Patent Application Laid-Open Publication No. 2003-8124    [Patent Citation 3]-   Japanese Patent Application Laid-Open Publication No. 2003-270551

DISCLOSURE OF INVENTION Technical Problems

For instance, it is necessary that an output power of a carbon dioxidelaser as a pulse laser beam is in the range of 10 to 20 kW in order toobtain an EUV light in the range of 100 to 200 W. In the case in which alaser beam of such a high output power is used, various optical elementsin a light path absorb a light and become high temperature, therebycausing a shape or a direction of a wave front of a laser beam isvaried. In the present specification, a wave front of a laser beamincludes a shape and a direction of a wave front of a laser beam.

In the case in which a laser beam of a high output power passes througha lens or a window, a shape or an index of refraction of the lens or thewindow is varied by an increase in a temperature due to a heatgeneration, whereby a wave front of the laser beam that has passedthrough is varied. For instance, in the case in which a wave front of alaser beam is varied, a laser beam cannot be effectively incident to anamplification region in a laser amplifier, whereby a desired laseroutput cannot be obtained. Moreover, since a focal position of a laserbeam that is incident into a chamber is varied corresponding to avariation of a wave front of a laser beam, a laser beam cannot beeffectively irradiated to a target material, whereby an output power ofan EUV light is reduced.

The present invention was made in consideration of the above problems,and an object of the present invention is to provide an extremeultraviolet light source device and a control method for an extremeultraviolet light source device in which a laser beam can be effectivelycorrected. Another object of the present invention is to provide anextreme ultraviolet light source device and a control method for anextreme ultraviolet light source device in which an optical performanceof a driver pulsed laser beam can be stabilized by correcting an opticalperformance of a guide laser beam on a steady basis. Another object ofthe present invention is to provide an extreme ultraviolet light sourcedevice and a control method for an extreme ultraviolet light sourcedevice in which a reliability can be improved without a complexity of adevice configuration by using a pre-pulsed laser beam together with aguide laser beam. Other objects of the present invention will beclarified by the explanation of the modes described later.

Solution of Problem

In order to solve the above problems of the conventional art, an extremeultraviolet light source device in accordance with a first aspect of thepresent invention is an extreme ultraviolet light source device thatgenerates an extreme ultraviolet light by irradiating a target materialwith a driver pulsed laser beam for turning the target material intoplasma, comprising a target material supply part that supplies thetarget material into a chamber; a driver laser device that outputs thedriver pulsed laser beam; an optical system that irradiates the targetmaterial in the chamber with the driver pulsed laser beam that is outputfrom the driver laser device; a guide laser device that outputs a guidelaser beam; a guide laser beam introduction part that introduces theguide laser beam into the optical system along a light path of thedriver pulsed laser beam; a guide laser beam detection part that detectsan optical performance of the guide laser beam that is introduced intothe optical system; a correction part that is disposed in the opticalsystem and that corrects the optical performance of the guide laserbeam; and a correction control part that controls the correction part insuch a manner that the optical performance that is detected by the guidelaser beam detection part is in a predetermined value.

Viewed from a second aspect, in the first aspect, the guide laser deviceoutputs the guide laser beam as a continuous light or a pseudocontinuous light, and the correction control part controls thecorrection part in such a manner that the optical performance is in apredetermined value in both of a period when the driver pulsed laserbeam is output and a period when the driver pulsed laser beam is notoutput.

Viewed from a third aspect, in the second aspect, the guide laser beamhas a beam diameter substantially equivalent to that of the driverpulsed laser beam and passes through a light path substantiallyequivalent to that of the driver pulsed laser beam.

Viewed from a fourth aspect, in the third aspect, a wavelength of theguide laser beam is specified to be smaller than that of the driverpulsed laser beam.

Viewed from a fifth aspect, in the fourth aspect, the guide laser beamis output as a guide laser beam in a single transverse mode.

Viewed from a sixth aspect, in any one of the first aspect to the fifthaspect, the optical system is provided with a transmission type opticalelement and a reflection type optical element, the transmission typeoptical element makes the driver pulsed laser beam and the guide laserbeam be transmitted, and the reflection type optical element makes thedriver pulsed laser beam and the guide laser beam be reflected.

Viewed from a seventh aspect, in any one of the first aspect to thefifth aspect, the guide laser beam introduction part is configured as afirst type guide laser beam introduction part that makes the guide laserbeam be transmitted and that makes the driver pulsed laser beam bereflected.

Viewed from an eighth aspect, in any one of the first aspect to thefifth aspect, the guide laser beam introduction part is configured as asecond type guide laser beam introduction part that makes the guidelaser beam be reflected and that makes the driver pulsed laser beam betransmitted.

Viewed from a ninth aspect, in any one of the first aspect to the fifthaspect, the guide laser beam introduction part is configured as a firsttype guide laser beam introduction part that makes the guide laser beambe transmitted and that makes the driver pulsed laser beam be reflected,or the guide laser beam introduction part is configured as a second typeguide laser beam introduction part that makes the guide laser beam bereflected and that makes the driver pulsed laser beam be transmitted,and any one of the first type guide laser beam introduction part and thesecond type guide laser beam introduction part is used depending on aninstallation position thereof in the optical system.

Viewed from a tenth aspect, in the ninth aspect, the optical systemincludes an amplifier that amplifies a laser beam, the second type guidelaser beam introduction part is used in the case in which the guidelaser beam introduction part is disposed on an input side of theamplifier, and the first type guide laser beam introduction part is usedin the case in which the guide laser beam introduction part is disposedon an output side of the amplifier.

Viewed from an eleventh aspect, in any one of the first aspect to thefifth aspect, the guide laser beam introduction part is configured by adiamond substrate made of a diamond and a coating that is formed on thediamond substrate, and the coating is configured as any one of a firsttype coating that makes the guide laser beam be transmitted and thatmakes the driver pulsed laser beam be reflected and a second typecoating that makes the guide laser beam be reflected and that makes thedriver pulsed laser beam be transmitted.

Viewed from a twelfth aspect, in any one of the first aspect to thefifth aspect, the guide laser beam introduction part is configured toinclude a rear mirror that configures a part of the driver laser pulsedoscillator, and the rear mirror is configured to make the driver pulsedlaser beam be reflected and to make the guide laser beam be transmitted.

Viewed from a thirteenth aspect, in any one of the first aspect to thefifth aspect, all of part which the guide laser beam passes through inthe optical system is made of a reflection type optical element exceptfor a laser window that is disposed in the chamber.

Viewed from a fourteenth aspect, in any one of the first aspect to thefifth aspect, the correction part corrects at least one of a wave frontshape and a direction of the guide laser beam.

Viewed from a fifteenth aspect, in any one of the first aspect to thefifth aspect, the correction part can be disposed on any one or both ofan output side and an input side for an amplifier or a saturableabsorber that are included in the optical system.

Viewed from a sixteenth aspect, in the first aspect, the extremeultraviolet light source device that generates an extreme ultravioletlight by irradiating a target material with a main pulsed laser beamafter with a pre-pulsed laser beam, further comprises a pre-pulsed laserdevice that outputs the pre-pulsed laser beam;

a pre-pulsed guide laser device that outputs the pre-pulsed guide laserbeam; a pre-pulsed optical system that irradiates the target materialwith the pre-pulsed laser beam; a pre-pulsed guide laser beamintroduction part that introduces the pre-pulsed guide laser beam intothe pre-pulsed optical system along a light path of the pre-pulsed laserbeam; a pre-pulsed guide laser beam detection part that detects anoptical performance of the pre-pulsed guide laser beam; a pre-pulsedcorrection part that is disposed in the pre-pulsed optical system andthat corrects the optical performance of the pre-pulsed guide laserbeam; and a pre-pulsed correction control part that controls thepre-pulsed correction part in such a manner that the optical performancethat is detected by the pre-pulsed guide laser beam detection part is ina predetermined value. The target material that has been irradiated withthe pre-pulsed laser beam is turned into, for example, any one of avapor state, a mixed state of plasma and a vapor, a weak plasma state,and a fine particle state.

An extreme ultraviolet light source device in accordance with aseventeenth aspect of the present invention is an extreme ultravioletlight source device that generates an extreme ultraviolet light byirradiating a target material with a main pulsed laser beam after with apre-pulsed laser beam, comprising a pre-pulsed laser device that outputsthe pre-pulsed laser beam; a pre-pulsed guide laser device that outputsthe pre-pulsed guide laser beam; a pre-pulsed optical system thatirradiates the target material with the pre-pulsed laser beam; apre-pulsed guide laser beam introduction part that introduces thepre-pulsed guide laser beam into the pre-pulsed optical system along alight path of the pre-pulsed laser beam; a pre-pulsed guide laser beamdetection part that detects an optical performance of the pre-pulsedguide laser beam; a pre-pulsed correction part that is disposed in thepre-pulsed optical system and that corrects the optical performance ofthe pre-pulsed guide laser beam; and a pre-pulsed correction controlpart that controls the pre-pulsed correction part in such a manner thatthe optical performance that is detected by the pre-pulsed guide laserbeam detection part is in a predetermined value.

Viewed from an eighteenth aspect, in the seventeenth aspect, thepre-pulsed guide laser device outputs the pre-pulsed guide laser beam asa continuous light or a pseudo continuous light, and the pre-pulsedcorrection control part can control the pre-pulsed correction part insuch a manner that the optical performance is in a predetermined valuein both of a period when the pre-pulsed laser beam is output and aperiod when the pre-pulsed laser beam is not output.

Viewed from a nineteenth aspect, in the first aspect, the guide laserdevice can also be used as a pre-pulsed laser device that irradiates thetarget material with the pre-pulsed laser beam prior to with the driverpulsed laser beam.

Viewed from a twentieth aspect, in the nineteenth aspect, the pre-pulsedlaser beam that is used together with the guide laser beam is outputfrom the pre-pulsed laser device in a period when the driver pulsedlaser beam is not output, and the pre-pulsed laser beam is specified tohave a beam diameter smaller than that of the driver pulsed laser beamand have an axis the same as that of the driver pulsed laser beam.

Viewed from a twenty-first aspect, in the nineteenth aspect, in the casein which the optical performance is corrected, the pre-pulsed laserdevice irradiates the target material with the pre-pulsed laser beam ata first output power that is specified in advance in such a manner thatthe target material is not physically varied even in the case in whichthe target material is irradiated with the pre-pulsed laser beam, and inthe case in which the target material is turned into plasma by thedriver pulsed laser beam, the pre-pulsed laser device irradiates thetarget material with the pre-pulsed laser beam at a second output powerlarger than the first output power, the second output power beingspecified in advance in such a manner that the target material isexpanded by a heat from the pre-pulsed laser beam.

Viewed from a twenty-second aspect, in the nineteenth aspect, in thecase in which the optical performance is corrected, the pre-pulsed laserdevice outputs the pre-pulsed laser beam at a timing when the targetmaterial is not irradiated, and in the case in which the target materialis turned into plasma by the driver pulsed laser beam, the pre-pulsedlaser device irradiates the target material with the pre-pulsed laserbeam.

Viewed from a twenty-third aspect, in the nineteenth aspect, thepre-pulsed laser beam is introduced to the optical system on adownstream side in a direction of travel of the laser beam for anamplification system that is disposed in the optical system by the guidelaser beam introduction part in such a manner that the pre-pulsed laserbeam has an axis the same as that of the driver pulsed laser beam.

Viewed from a twenty-fourth aspect, in the nineteenth aspect, adownstream side of an amplification system that is disposed in theoptical system is a light focusing optical system for focusing thedriver pulsed laser beam and the pre-pulsed laser beam into apredetermined position, the guide laser beam introduction part isconfigured to be provided with: a first beam splitter that is disposedat an inlet of the light focusing optical system, that makes thepre-pulsed laser beam be transmitted, and that makes the driver pulsedlaser beam be reflected; and a second beam splitter that is disposedbetween the first beam splitter and the pre-pulsed laser device, thatmakes the pre-pulsed laser beam be transmitted, and that makes a returnlight of the pre-pulsed laser beam that is reflected by the targetmaterial and that returns in the light focusing optical system bereflected, and a light focusing optical system control part is disposedfor controlling the light focusing optical system based on a signaltransmitted from a return light detection part that detects the returnlight.

A control method in accordance with a twenty-fifth aspect of the presentinvention is a control method for controlling an optical performance ofa laser beam that is used for an extreme ultraviolet light sourcedevice, comprising the steps of continuously outputting a guide laserbeam that travels along a light path of a driver pulsed laser beam thatis irradiated to a target material to turn the target material intoplasma in both of a period when the driver pulsed laser beam is outputand a period when the driver pulsed laser beam is not output; detectingan optical performance of the guide laser beam; and correcting thedetected optical performance of the guide laser beam to be apredetermined value.

A control method in accordance with a twenty-sixth aspect of the presentinvention is a control method for controlling an optical performance ofa laser beam that is used for an extreme ultraviolet light sourcedevice, comprising the steps of outputting a pre-pulsed laser beam thatis irradiated to a target material prior to a driver pulsed laser beamalong a light path of the driver pulsed laser beam; detecting an opticalperformance of the pre-pulsed laser beam; correcting the detectedoptical performance of the pre-pulsed laser beam to be a predeterminedvalue; irradiating the target material with the pre-pulsed laser beam toexpand the target material; and generating an extreme ultraviolet lightby irradiating the expanded target material with the driver pulsed laserbeam to turn the target material into plasma.

A pulsed laser device in accordance with a twenty-seventh aspect of thepresent invention is a laser pulsed device that oscillates a pulsedlaser beam and a pulsed laser device that amplifies the pulsed laserbeam that is output from the laser pulsed device to output the pulsedlaser beam, the pulsed laser device comprising a guide laser device thatoutputs a guide laser beam; a guide laser beam introduction part thatintroduces the guide laser beam into the optical system along a lightpath of the pulsed laser beam; a guide laser beam detection part thatdetects an optical performance of the guide laser beam that isintroduced into the optical system; a correction part that is disposedin the optical system and that corrects the optical performance of theguide laser beam; and a correction control part that controls thecorrection part in such a manner that the optical performance that isdetected by the guide laser beam detection part is in a predeterminedvalue.

Viewed from a twenty-eighth aspect, in the twenty-seventh aspect, theguide laser device can also be used as a pre-pulsed laser device thatirradiates a pre-pulsed laser beam that is irradiated to the targetmaterial prior to the driver pulsed laser beam.

A combination other than the combinations that have been explicitlyshown in the above descriptions can also be included in the scope of thepresent invention.

Advantageous Effects of Invention

By the present invention, a guide laser beam is introduced into theoptical system along a light path of a driver pulsed laser beam, and theguide laser beam is corrected in such a manner that an opticalperformance of the guide laser beam is in a predetermined value.Consequently, even in the case in which an optical performance is varieddue to a heat load or a mechanical vibration, the correction can becarried out immediately, and the driver pulsed laser beam can bestabilized to be irradiated to a target material. By this configuration,a reliability of an extreme ultraviolet light source device can beimproved.

By the present invention, since a guide laser beam is output as acontinuous light or a pseudo continuous light, the guide laser beam canbe corrected in both of a period when the driver pulsed laser beam isoutput and a period when the driver pulsed laser beam is not output. Afeedback control for an optical performance of the guide laser beam canbe carried out on a steady basis. Consequently, in the case in which aheat caused by the driver pulsed laser beam is varied on a grand scaleor in the case in which the driver pulsed laser beam is output after astoppage over a long period of time for instance, an optical performanceof the driver pulsed laser beam can be stabilized by an immediatefollow-up.

By the present invention, a pre-pulsed laser beam that is used forexpanding a target material can also be used as a guide laser beam.Consequently, a reliability of an extreme ultraviolet light sourcedevice can be improved without complicating the configuration of theextreme ultraviolet light source device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an extreme ultraviolet light sourcedevice in accordance with a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the state in which only a guidelaser beam is output.

FIG. 3 is a flowchart of a wave front correction processing.

FIG. 4 is a flowchart of a processing in which a laser controllernotifies an EUV controller of an adjustment completion.

FIG. 5 is a block diagram showing an extreme ultraviolet light sourcedevice in accordance with a second embodiment of the present invention.

FIG. 6 is a flowchart of a wave front correction processing.

FIG. 7 is a block diagram showing an extreme ultraviolet light sourcedevice in accordance with a third embodiment of the present invention.

FIG. 8 is a block diagram showing an EUV chamber.

FIG. 9 is a block diagram showing a wave front correction part.

FIG. 10 is a block diagram showing a sensor.

FIG. 11 is a block diagram showing an isolator.

FIG. 12 is an explanatory diagram showing the state in which only aguide laser beam is output.

FIG. 13 is a flowchart of a wave front correction processing.

FIG. 14 is a block diagram showing an extreme ultraviolet light sourcedevice in accordance with a fourth embodiment of the present invention.

FIG. 15 is an explanatory diagram showing the state in which only aguide laser beam is output.

FIG. 16 is an explanatory diagram showing a configuration example forintroducing a guide laser beam in accordance with a fifth embodiment ofthe present invention.

FIG. 17 is an explanatory diagram showing another example forintroducing a guide laser beam.

FIG. 18 is an explanatory diagram showing furthermore another examplefor introducing a guide laser beam.

FIG. 19 is an explanatory diagram showing an example of an arrangementfor a wave front correction part and a sensor in accordance with a sixthembodiment of the present invention.

FIG. 20 is an explanatory diagram showing another example of anarrangement for a wave front correction part and a sensor.

FIG. 21 is a block diagram showing a wave front curvature correctionpart in accordance with a seventh embodiment of the present invention.

FIG. 22 is a block diagram showing a wave front curvature correctionpart in accordance with an eighth embodiment of the present invention.

FIG. 23 is a block diagram showing a wave front curvature correctionpart in accordance with a ninth embodiment of the present invention.

FIG. 24 is a block diagram that follows FIG. 23.

FIG. 25 is a block diagram showing a wave front curvature correctionpart in accordance with a tenth embodiment of the present invention.

FIG. 26 is a block diagram that follows FIG. 25.

FIG. 27 is a block diagram showing a wave front curvature correctionpart in accordance with an eleventh embodiment of the present invention.

FIG. 28 is a block diagram showing a wave front correction part inaccordance with a twelfth embodiment of the present invention.

FIG. 29 is a block diagram showing a wave front correction part inaccordance with a thirteenth embodiment of the present invention.

FIG. 30 is a block diagram showing a wave front correction part inaccordance with a fourteenth embodiment of the present invention.

FIG. 31 is a block diagram showing a wave front correction part inaccordance with a fifteenth embodiment of the present invention.

FIG. 32 is a block diagram showing a sensor in accordance with asixteenth embodiment of the present invention.

FIG. 33 is a block diagram showing a sensor in accordance with aseventeenth embodiment of the present invention.

FIG. 34 is a block diagram showing a sensor in accordance with aneighteenth embodiment of the present invention.

FIG. 35 is a block diagram showing a substantial part of a chamber inaccordance with a nineteenth embodiment of the present invention.

FIG. 36 is a block diagram showing an optical sensor part in accordancewith a twentieth embodiment of the present invention.

FIG. 37 is a block diagram showing an optical sensor part in accordancewith a twenty-first embodiment of the present invention.

FIG. 38 is a block diagram showing an optical sensor part in accordancewith a twenty-second embodiment of the present invention.

FIG. 39 is a block diagram showing a light receiving element.

FIG. 40 is an explanatory diagram showing a relationship between a beamshape of a laser beam and an output power of a light receiving element.

FIG. 41 is a block diagram showing an optical sensor part in accordancewith a twenty-third embodiment of the present invention.

FIG. 42 is a block diagram that follows FIG. 41.

FIG. 43 is a block diagram that follows FIG. 42.

FIG. 44 is a block diagram showing an extreme ultraviolet light sourcedevice in accordance with a twenty-fourth embodiment of the presentinvention.

FIG. 45 is a block diagram showing an extreme ultraviolet light sourcedevice in accordance with a twenty-fifth embodiment of the presentinvention.

FIG. 46 is a view showing the state in which only a driver pulsed laserbeam is output.

FIG. 47 is a schematic explanatory diagram showing a relationship amonga driver pulsed laser beam, a pre-pulsed laser beam, and a targetmaterial.

FIG. 48 is a flowchart of a wave front correction processing.

FIG. 49 is a flowchart of a processing in which a laser controllernotifies an EUV light source controller of an adjustment completion.

FIG. 50 is a block diagram showing an extreme ultraviolet light sourcedevice in accordance with a twenty-sixth embodiment of the presentinvention.

FIG. 51 is a block diagram showing an extreme ultraviolet light sourcedevice in accordance with a twenty-seventh embodiment of the presentinvention.

FIG. 52 is a block diagram showing an extreme ultraviolet light sourcedevice in accordance with a twenty-eighth embodiment of the presentinvention.

FIG. 53 is a block diagram showing an extreme ultraviolet light sourcedevice in accordance with a twenty-ninth embodiment of the presentinvention.

FIG. 54 is a block diagram showing an extreme ultraviolet light sourcedevice in accordance with a thirtieth embodiment of the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

A mode for the present invention will be described below in detail withreference to the drawings. In the mode for the present invention, anoptical performance of a guide laser beam is corrected by supplying aguide laser beam at a predetermined timing on a light path substantiallyequivalent to that of a driver pulsed laser beam as described in thefollowing. The optical performance means any one or both of a wave frontshape and a direction of travel for a laser beam.

Embodiment 1

A first embodiment of the present invention will be described in thefollowing with reference to FIGS. 1 to 4. FIG. 1 is an explanatorydiagram showing a general configuration of an extreme ultraviolet lightsource device 1.

An extreme ultraviolet light source device 1 can be configured to beprovided with, for example, a chamber 10 that generates an EUV light, adriver pulse laser light source device 2 that supplies a driver pulselaser light to the chamber 10, and an EUV light source controller 80.

The driver pulse laser light source device 2 can be configured to beprovided with, for example, a driver laser oscillator (MasterOscillator) 20 that decides a time waveform and a repetition rate of alaser pulse, an amplification system 30, a light focusing system 40, awave front correction controller 60, and a laser controller 70. Theextreme ultraviolet light source device 1 supplies an EUV light to anEUV exposure device 5. In the figure, the driver laser oscillator 20 andthe wave front correction controller 60 are described as MO and WFC-C,respectively.

The outline of the chamber 10 will be described at first. The chamber 10can be configured to be provided with, for example, a chamber body 11, aconnection part 12 with the EUV exposure device 5, a window 13, an EUVlight collector mirror 14, and a target material supply unit 15.

The chamber body 11 is kept to be in a vacuum state by a vacuum pumpthat is not shown in the figure. The chamber body 11 can be configuredto be provided with, for example, a mechanism that collects debris thatis not shown.

The connection part 12 is configured to connect between the chamber 10and the EUV exposure device 5. An EUV light that is generated in thechamber body 11 is supplied to the EUV exposure device 5 via theconnection part 12.

The window 13 is disposed on the chamber body 11. A driver pulsed laserbeam that is emitted from the driver pulse laser light source device 2is incident to the chamber body 11 through the light focusing system 40via the window 13.

The EUV light collector mirror 14 is a mirror that reflects an EUV lightand collects the EUV light into an intermediate focus (IF). Theintermediate focus (IF) is set in the connection part 12. The EUV lightcollector mirror 14 is configured, for instance, as a concave face likea spheroid that does not ideally generate an aberration in order tocarry out a transcription and an image formation for an image of aplasma luminous point into the IF. For instance, a multilayer coatingcomposed of a molybdenum coating and a silicon coating is formed on thesurface of the EUV light collector mirror 14. By this configuration, anEUV light having a wavelength of approximately 13.5 nm can be reflected.

The target material supply part 15 supplies a target material such astin in a state of liquid, solid, or gas. A tin compound such as stannane(SnH4) can also be used. In the case in which tin is supplied in a stateof liquid, it is possible to adopt a method for supplying a solutionthat includes tin or for supplying a colloid solution that includes tinor a tin compound as well as a method for heating pure tin to a meltingpoint to liquefy the tin. In the present embodiment, a droplet DP of tinis described for example as a target material. However, a targetmaterial of the present invention is not limited to a tin droplet, andother materials such as lithium (Li) and xenon (Xe) can also be used.

A behavior in the chamber 10 will be briefly described at first. Adriver pulsed laser beam L1 is configured to be focused on thepredetermined point in the chamber body 11 via the window 13 forincidence. The target material supply part 15 drops a tin droplet DPtoward the predetermined point. At the timing when the tin droplet DPreaches the predetermined point, the driver pulsed laser beam L1 of apredetermined output power is output from the driver pulse laser lightsource device 2. The tin droplet DP is irradiated with the driver pulsedlaser beam L1 to be plasma PLZ. The plasma PLZ emits an EUV light L2.The EUV light L2 is collected into the intermediate focus IF in theconnection part 12 by the EUV light collector mirror 14 and is suppliedto the EUV exposure device 5.

In the next place, the configuration of the driver pulse laser lightsource device 2 will be described. The driver pulse laser light sourcedevice 2 is configured as a carbon dioxide pulse laser light sourcedevice, and carries out a pulsed output of the driver pulsed laser beamL1 having the specifications of a wavelength of 10.6 μm, a singletransverse mode, a repetition rate of 100 kHz, 100 to 200 mJ, and 10 kWto 20 kW.

A laser beam that is output from the driver laser oscillator 20 isamplified by the amplification system 30 and is transmitted to the lightfocusing system 40. The light focusing system 40 supplies the driverpulsed laser beam L1 into the chamber 10. The light focusing system 40is configured to be provided with, for example, a reflecting mirror 41,an off-axis parabolic concave mirror 42, and a relay optical system 43.It is preferable that the relay optical system 43 and a relay opticalsystem 31 described later are configured as a reflection type opticalsystem. In the following descriptions, using a direction of travel for alaser beam as a standard, a side of the driver laser oscillator 20 isreferred to as an upstream side, and a side of the chamber 10 isreferred to as a downstream side in some cases.

The amplification system 30 is configured to be provided with, forexample, relay optical systems 31 (1) and 31 (2), a preamplifier 32, awave front correction part 34, a main amplifier 35, and a guide laserbeam introduction mirror (a guide laser beam introduction part) 52.

The relay optical systems 31 (1) and 31 (2) are optical systems thatadjust a spread angle of a beam and a size of a beam for a laser beamthat is output from the driver laser oscillator 20 to efficiently fillan amplification region in the preamplifier 32 with a laser beam that isemitted from the driver laser oscillator 20. In the case in which it isnot required to distinguish the relay optical systems 31 (1) and 31 (2)in particular, the relay optical systems 31 (1) and 31 (2) are referredto as a relay optical system 31. The relay optical system 31 expands abeam diameter of a laser beam that is output from the driver laseroscillator 20, and converts the laser beam into a predetermined beamlight flux.

The preamplifier 32 amplifies an incident laser beam and emits theamplified laser beam. The laser beam that has been amplified by thepreamplifier 32 is input to the wave front correction part 34 via therelay optical system 31 (2).

For the relay optical system 31 and the preamplifier 32, an optical axisof a laser beam may be out of alignment or a wave front shape of a laserbeam may be varied due to a heat, a vibration or the like in some cases.In the case in which a laser beam of which an optical performance is outof the predetermined expected value is input to the main amplifier 35,an expected amplification operation cannot be obtained.

Consequently, in the present embodiment, the wave front correction part34 as a “correction port” is disposed on the input side of the mainamplifier 35. In the figure, the wave front correction port is indicatedas a WFC (Wave Front Compensator). The principle of the wave frontcorrection part 34 will be described in FIG. 9.

A laser beam that has been corrected by the wave front correction part34 is input into the main amplifier 35 for being amplified, and istransmitted to the light focusing system 40. The light focusing system40 makes a laser beam to be irradiated toward the predetermined positionin the chamber 10.

The present embodiment is provided with a configuration for introducinga guide laser beam for a correction on a light path substantiallyequivalent to that of a driver pulsed laser beam. The configurationincludes, for example, a guide laser device 50 for outputting a guidelaser beam, a laser collimator 51, and a guide laser beam introductionmirror 52.

A guide laser beam L3 is a laser beam that is used for correcting theoptical system, and plays a leading role. The guide laser device 50outputs, for example, a helium neon laser in a single transverse mode asa guide laser beam. In the figure, the guide laser device is indicatedas CW.

A guide laser beam can be configured as a laser beam of a continuouslight or a pseudo continuous light, or as a pulsed laser beam thatcarries out a pulse light emission with a high repetition rate such as aYAG (Yttrium Aluminum Garnet laser). Moreover, a visible light laser ofa continuous oscillation can also be used as a guide laser beam.

A guide laser beam in accordance with the present embodiment isconfigured to travel on a light path substantially equivalent to that ofa driver pulsed laser beam, and is configured to have a beam diametersubstantially equivalent to that of a driver pulsed laser beam. Theguide laser beam that has been output from the guide laser device 50 isincident to the guide laser beam introduction mirror 52 via the lasercollimator 51.

The guide laser beam introduction mirror 52 is configured as a “secondtype” guide laser beam introduction mirror that makes the guide laserbeam be reflected and that makes the driver pulsed laser beam betransmitted. A guide laser beam that has been reflected by the guidelaser beam introduction mirror 52 travels in an optical system at anoptical axis equivalent to that of a driver pulsed laser beam, and isincident to the main amplifier 35 via the wave front correction part 34.

The guide laser beam L3 passes through the main amplifier 35, and isthen incident to the chamber 10 via the relay optical system 43, themirrors 41 and 42, the sensor 44, and the window 13 to be absorbed intoa dumper 19.

The sensor 44 detects a wave front shape and a direction of travel for aguide laser beam, and outputs them to the wave front correctioncontroller 60. An example of the sensor 44 (or the sensor 36 (see FIG.5)) will be described in another embodiment.

FIG. 2 is an explanatory diagram showing the state in which only a guidelaser beam is output. As described above, a pulsed output is carried outfor a driver pulsed laser beam, and a continuous output is carried outfor a guide laser beam. Consequently, a guide laser beam is output evenin the period when a driver pulsed laser beam is not output.

A guide laser beam L3 is affected by an error that occurs in opticalsystems (34, 35, and 40) by traveling on a light path substantiallyequivalent to that of a driver pulsed laser beam. An adverse affect thatis applied to a guide laser beam is detected by a sensor 44 that isdisposed at the final exit of a laser beam. The wave front correctioncontroller 60 controls the wave front correction part 34 based on thedetection signal transmitted from the sensor 44, and corrects adirection of travel and a wave front shape for a guide laser beam.

Consequently, a driver pulsed laser beam is supplied into the chamber 10and irradiated to a target material while having a stable opticalperformance with less adverse affect caused by a heat load by passingthrough the wave front correction part 34 that has been corrected by aguide laser beam.

The control system will be described in the following. As shown in FIG.1, an extreme ultraviolet light source device 1 is configured to beprovided with the wave front correction controller 60, the lasercontroller 70, and the EUV light source controller 80.

FIG. 3 is a flowchart showing a correction processing that is carriedout by the wave front correction controller 60. The present processingis carried out in at least one of a period before a driver pulsed laserbeam is output (on an activation of the extreme ultraviolet light sourcedevice 1), a period when a driver pulsed laser beam is output, and aninterval period when an output of a driver pulsed laser beam is stopped.In the present embodiment, the processing can be carried out in theabove periods since a guide laser beam is configured as a continuouslight or a pseudo continuous light. In other words, a continuousfeedback control for an optical performance of a laser beam can becarried out during an operation of the extreme ultraviolet light sourcedevice 1.

Each flowchart that will be described in the following shows the summaryof each processing, and may be different from an actual computer programin some cases. Moreover, those skilled in the art can modify or delete astep that is shown in the figure, and can add a new step. A direction ofa laser beam is referred to as an “angle” in some cases in thefollowing.

The wave front correction controller 60 acquires a measured value Dafrom the sensor 44 (S10), and calculates a deviation ΔD that is adifference between a target value Dset and a measured value Da (S11).The wave front correction controller 60 judges whether or not anabsolute value of the deviation AD is equivalent to or less than apredetermined permissible value Dth (S12). For instance, a permissiblevalue Dth is specified as a value that does not affect an amplificationcharacteristic of a laser beam.

In the case in which a difference ΔD between a target value and ameasured value is equivalent to or less than a permissible value Dth(S12: YES), the wave front correction controller 60 outputs anirradiation OK signal to the laser controller 70 (S13). The irradiationOK signal is an adjustment completion signal that means a wave front ofa laser beam has been adjusted to be a predetermined wave front (acurvature and a direction). The wave front correction controller 60 thentransits to the step S14, and carries out a high precision stabilizingoperation. The high precision stabilizing operation is an operation forcarrying out a correction for clearing a difference ΔD with a targetvalue with a high degree of accuracy. By the step S14, the irradiationOK signal can be maintained in an output enabled state on a constantbasis unless a large disturbance occurs once the irradiation OK signalis output in the step 13.

On the other hand, in the case in which an absolute value of ΔD exceedsa permissible value Dth (S12: NO), the wave front correction controller60 outputs an irradiation NG signal to the laser controller 70 (S15).The wave front correction controller 60 then makes the wave frontcorrection part 34 to carry out a correcting operation (S16). Theirradiation NG signal is an adjustment incomplete signal that means awave front of a laser beam has not been adjusted to be a predeterminedwave front. The wave front correction part 34 operates an anglecorrection part 100 and a wave front curvature correction part 200according to a drive signal transmitted from the wave front correctioncontroller 60 (see FIG. 9). By carrying out a correcting operation onceor a plurality of times, a wave front of a laser beam conforms to apredetermined wave front.

FIG. 4 is a flowchart showing an operation of the laser controller 70and an operation of the EUV light source controller 80. In the case inwhich the laser controller 70 receives an irradiation OK signal from thewave front correction controller 60 (S20: YES), the laser controller 70notifies the EUV light source controller 80 of that an adjustment of thedriver pulse laser light source device 2 has been completed (S21).

In the case in which the EUV light source controller 80 receives anadjustment completion notice from the laser controller 70, the EUV lightsource controller 80 outputs a light emission command to the lasercontroller 70. The light emission command is a command or an electricalsignal that instructs to output a driver pulsed laser beam.

The laser controller 70 stops an output of a driver pulsed laser beamand stands by until a light emission command is output from the EUVlight source controller 80 (S22: NO, S24). In the case in which thelaser controller 70 receives a light emission command (S22: YES), thelaser controller 70 outputs a driver pulsed laser beam L1 from thedriver laser oscillator 20.

The driver pulsed laser beam L1 is amplified by the amplification system30, and is then incident to the chamber 10 via the light focusing system40. The droplet DP is irradiated with the driver pulsed laser beam L1 tobe the plasma PLZ. The EUV light L2 that is emitted from the plasma PLZis collected into the intermediate focus IF by the EUV light collectormirror 14 and is transmitted to the EUV exposure device 5.

In the present embodiment as described above, the guide laser beam L3 ofa continuous light is introduced to a light path of the driver pulsedlaser beam L1, and an operation of the wave front correction part 34 iscontrolled based on a measured result of an optical performance of aguide laser beam. Consequently, even in the case in which thecharacteristics of the optical system are varied due to a heat, avibration or the like, the variation can be corrected in a rapid manner,and an expected driver pulsed laser beam can be stably irradiated to atarget material. As a result, a reliability of the extreme ultravioletlight source device 1 can be improved.

In the present embodiment, a guide laser beam is oscillated on a steadybasis, and a direction of travel and a wave front shape of a laser beamcan be adjusted on a steady basis. Consequently, even in the case inwhich an output of the driver pulsed laser beam varies or even in thecase in which the driver pulsed laser beam is output immediately afteran output of the driver pulsed laser beam is stopped for an extendedperiod of time for instance, the driver pulsed laser beam having astable output and a focusing performance can be obtained.

It is preferable that the guide laser beam introduction mirror 52 isfabricated by using a substrate made of a diamond having an excellentthermal conductivity. However, for a region in which a heat load isrelatively small such as an upstream side of the driver pulsed laserbeam (for instance, a region between the oscillator 20 and thepreamplifier 32), a substrate made of alkali halide such as BaF2, KCl,and NaCl, or a substrate made of a crystal of alkali earth halide canalso be used.

Embodiment 2

A second embodiment of the present invention will be described in thefollowing with reference to FIGS. 5 and 6. Each embodiment that will bedescribed in the following corresponds to a modified example of thefirst embodiment. Consequently, points different from the firstembodiment will be described mainly. In the present embodiment, theconfigurations that correct a laser beam (34, 36, and 44, 45) aredisposed for both of a mechanism 30 that amplifies the driver pulsedlaser beam and a mechanism 40 that focuses the driver pulsed laser beaminto a predetermined position.

FIG. 5 is an explanatory diagram showing a general configuration of anextreme ultraviolet light source device 1 in accordance with the secondembodiment of the present invention. In the present embodiment, a wavefront correction part 34 and a sensor 36 are disposed in theamplification system 30, and another wave front correction part 45 andanother sensor 44 are disposed in the light focusing system 40.

A first wave front correction controller 60 (1) controls a correction inthe amplification system 30, and a second wave front correctioncontroller 60 (2) controls a correction in the light focusing system 40.

FIG. 6 is a flowchart showing an operation in accordance with thepresent embodiment. In the present embodiment, a curvature and adirection of a wave front of a laser beam is corrected in order from anupstream side. At first, the wave front correction controller 60 (1)that controls the wave front correction part 34 in the amplificationsystem 30 acquires a measured value Da1 from the sensor 36 (S30), andcalculates a deviation ΔD1 (S31).

The wave front correction controller 60 (1) judges whether or not anabsolute value of the deviation ΔD1 is equivalent to or less than apermissible value DTh1 (S32). In the case in which an absolute value ofthe deviation ΔD1 is equivalent to or less than the permissible valueDTh1 (S32: YES), the wave front correction controller 60 (1) outputs anOK signal 1 to the laser controller 70 (S33). The wave front correctioncontroller 60 (1) then carries out a high precision stabilizingoperation in the step S36, and returns to the step S30.

On the other hand, in the case in which an absolute value of thedeviation ΔD1 exceeds a permissible value DTh1 (S32: NO), the wave frontcorrection controller 60 (1) outputs an NG signal 1 to the lasercontroller 70 (S35). The wave front correction controller 60 (1) thendirects an execution of a correcting operation to the wave frontcorrection part 34 in such a manner that a difference ΔD1 between atarget value Dset1 and a measured value Da1 is reduced (S35). The wavefront correction controller 60 (1) then returns to the first step S30.

In the case in which the laser controller 70 receives the OK signal 1from the wave front correction controller 60 (1) (S40: YES), the lasercontroller 70 notifies the wave front correction controller 60 (2) thatmanages the wave front correction part 45 of that the wave frontcorrection of the former step has been completed (S41). The notificationis indicated as the “OK signal 1” in FIG. 6.

The wave front correction controller 60 (2) acquires a measured valueDa2 from the sensor 44 (S50), and calculates a deviation ΔD2 that is adifference between a target value Dset2 and a measured value Da2 (S51).The wave front correction controller 60 (2) judges whether or not thenotification of that the correcting operation of the former step hasbeen completed is received from the laser controller (S52).

Until the wave front correction of the former step that is carried outby the wave front correction controller 60 (1) is completed (S52), theexecution of the above steps S50 and S51 is repeated. In the case inwhich the wave front correction of the former step that is carried outby the wave front correction controller 60 (1) is completed (S52: YES),the wave front correction controller 60 (2) judges whether or not anabsolute value of the deviation ΔD2 that has been calculated in the stepS51 is equivalent to or less than a permissible value DTh2 (S53).

In the case in which an absolute value of the deviation ΔD2 isequivalent to or less than the permissible value DTh2 (S53: YES), thewave front correction controller 60 (2) outputs an OK signal 2 to thelaser controller 70 (S54). The wave front correction controller 60 (2)then carries out a high precision stabilizing operation in the next stepS57, and returns to the step S50. On the other hand, in the case inwhich an absolute value of the deviation ΔD2 exceeds a permissible valueDTh2 (S53: NO), the wave front correction controller 60 (2) outputs adrive signal to the wave front correction part 45 to make the wave frontcorrection part 45 to correct a curvature and a direction of a wavefront of a laser beam (S56). The wave front correction controller 60 (2)then returns to the first step S50.

In the case in which the laser controller 70 receives the OK signal 2from the second wave front correction controller 60 (2) (S42: YES), thelaser controller 70 notifies the EUV light source controller 80 of thatan adjustment of the driver pulse laser light source device 2 has beencompleted (S43).

In the case in which the laser controller 70 receives a light emissioncommand from the EUV light source controller 80, the laser controller 70makes the driver laser oscillator 20 to output a driver pulsed laserbeam (S44).

The present embodiment that is configured as described above outputs aguide laser beam regardless of whether a driver pulsed laser beam isoutput or not, that is, in an asynchronous manner with a driver pulsedlaser beam, and carries out a feedback control in such a manner that anoptical performance of a laser beam is in the predetermined value.Consequently, the present embodiment has an operation effect equivalentto that of the first embodiment.

Moreover, in the present embodiment, since an optical performance of alaser beam is corrected individually for both of the amplificationsystem 30 and the light focusing system 40, both of an amplifyingperformance and a light focusing performance can be stabilized, wherebya reliability can be further improved as compared with the firstembodiment.

Moreover, in the present embodiment, after it is confirmed that a wavefront correction processing is completed on an upstream side (in theamplification system), a wave front correction processing is carried outon a downstream side (in the light focusing system). Consequently, awave front correction that is carried out by the wave front correctioncontroller 60 (1) and a wave front correction that is carried out by thewave front correction controller 60 (2) can be prevented from competingagainst each other before it occurs.

Embodiment 3

A third embodiment of the present invention will be described in thefollowing with reference to FIGS. 7 to 12. In the present embodiment, aguide laser beam is introduced on an input side of the first amplifier32 (1). Moreover, in the present embodiment, the wave front correctionparts 34 (1), 34 (2), 34 (3), and 34 (4) are corresponded to theamplifiers 32 (1), 32 (2), 35 (1), and 35 (2), respectively, and a wavefront correction of a laser beam is carried out every when a laser beamis amplified.

FIG. 7 is a general block diagram showing an extreme ultraviolet lightsource device 1 in accordance with the third embodiment of the presentinvention. In the present embodiment, two slab type preamplifiers 32 (1)and 32 (2) are used as a preamplifier. A laser beam travels on a zigzaglight path included in the slab type preamplifiers 32 (1) and 32 (2) tobe amplified. Moreover, in the present embodiment, a plurality of mainamplifiers 35 (1) and 35 (2) are also disposed.

The saturable absorbers 33 (1) and 33 (2) are disposed on an output sideof the preamplifiers 32 (1) and 32 (2), respectively. The saturableabsorber is referred to as SA (Saturable Absorber) in the following. TheSAs 33 (1) and 33 (2) are elements that have a function in which a laserbeam having a light intensity equivalent to or larger than apredetermined threshold value can pass through the SA and a laser beamhaving a light intensity less than a predetermined threshold valuecannot pass through the SA.

The SAs 33 (1) and 33 (2) absorb a laser beam that returns from thechamber 10 (a return light) and a parasitic oscillation light and a selfoscillation light that are generated by the main amplifiers 35 (1) and35 (2). By the above configuration, the preamplifier 32 and the driverlaser oscillator 20 can be prevented from being damaged. Moreover, theSAs 33 (1) and 33 (2) play a role of suppressing a pedestal to improve aquality of a pulse waveform of a laser beam. The pedestal is a smallpulse that is generated temporally close to a main pulse.

A spatial filter 37 for improving a spatial transverse mode is disposedon an output side of the driver laser oscillator 20. The SA 33 (1) isdisposed at the exit of the preamplifier 32 (1), and the SA 33 (2) isdisposed at the exit of the next preamplifier 32 (2).

The wave front correction part 34 (1) and a sensor 36 (1) are disposedon a downstream side (an outgoing side of a laser beam) of the first SA33 (1). The wave front correction part 34 (2) and a sensor 36 (2) aredisposed on a downstream side of the second SA 33 (2).

A laser beam that has passed through the sensor 36 (2) is reflected bythe reflecting mirrors 38 (1) and 38 (2), and is incident to the wavefront correction part 34 (3). The wave front correction part 34 (3) isdisposed on an upstream side (an incident side of a laser beam) of themain amplifier 35 (1). A sensor 36 (3) corresponded to the wave frontcorrection part 34 (3) is disposed on a downstream side of the mainamplifier 35 (1).

The wave front correction part 34 (4) is disposed on an upstream side ofthe last main amplifier 35 (2). A sensor 36 (4) is disposed on adownstream side of the main amplifier 35 (2).

Similarly to the second embodiment, a mechanism that focuses the driverpulsed laser beam is provided with a wave front correction part 45 and asensor 44. Moreover, in the present embodiment, a polarization splittype isolator 46 is disposed between the reflecting mirrors 41 (1) and41 (2). The isolator 46 will be described later in FIG. 11.

A flow of a laser beam will be briefly described in the following. Atfirst, a laser beam that has been output from the driver laseroscillator 20 is transmitted to the spatial filter 37 to improve aspatial transverse mode. The laser beam in which a spatial transversemode has been improved passes through the guide laser beam introductionmirror 52, and is incident to an incident window of the slab typepreamplifier 32 (1). The laser beam passes in a zigzag manner betweentwo concave mirrors 42 to be amplified, and is emitted from an outgoingwindow.

The laser beam that has been amplified by the preamplifier 32 (1) passesthrough the SA 33 (1). By this configuration, a laser beam having alight intensity equivalent to or less than a predetermined thresholdvalue is eliminated. Due to the passing through the SA 33 (1), a wavefront shape of a laser beam is affected and may be out of an expectedvalue in some cases. Consequently, an optical performance (a wave frontshape and a direction) of a laser beam is corrected by the wave frontcorrection part 34 (1). The wave front correction controller 60 (1)detects a state of a laser beam that has been corrected based on ameasured value transmitted from the sensor 36 (1), and controls the wavefront correction part 34 (1) in such a manner that an opticalperformance of a laser beam is in a predetermined value.

The laser beam that has been corrected by the wave front correction part34 (1) is input to the second preamplifier 32 (2) to be amplified, andpasses through the SA 33 (2). The laser beam that has passes through theSA 33 (2) is corrected for a wave front by the wave front correctionpart 34 (2) similarly to the above. The wave front correction controller60 (2) outputs a drive signal to the wave front correction part 34 (2)in such a manner that a curvature and an angle of a wave front of alaser beam are in a predetermined value based on a measured valuetransmitted from the sensor 36 (2).

The laser beam that has been corrected by the wave front correction part34 (2) is incident to the wave front correction part 34 (3) via the tworeflecting mirrors 38 (1) and 38 (2). The wave front correctioncontroller 60 (3) controls the wave front correction part 34 (3) basedon a measured value transmitted from the sensor 36 (3) that is disposedon the exit side of the main amplifier 35 (1). The wave front correctioncontroller 60 (3) operates the wave front correction part 34 (3) in sucha manner that a wave front that can efficiently fill a laseramplification region in the main amplifier 35 (1) with a laser beam canbe obtained.

The laser beam that has been corrected by the wave front correction part34 (3) is incident to the wave front correction part 34 (4) afterpassing through the main amplifier 35 (1) and the sensor 36 (3).Similarly to the descriptions related to the wave front correction part34 (3), the wave front correction controller 60 (4) controls the wavefront correction part 34 (4) based on a measured value transmitted fromthe sensor 36 (4) that is disposed on the exit side of the mainamplifier 35 (2) in such a manner that an optical performance of a laserbeam that is incident to the main amplifier 35 (2) is in a predeterminedvalue.

As described above, in the present embodiment, a laser beam is amplifiedfour times and an optical performance of the laser beam is correctedfour times in the process for amplifying a laser beam. By thisconfiguration, a laser beam of a high output power that is emitted fromthe main amplifier 35 (2) of the final stage can be stabilized.

The laser beam that has been amplified is transmitted to the lightfocusing process, and is input to the wave front correction part 45. Thewave front correction controller 60 (5) makes the wave front correctionpart 45 to carry out a wave front correction based on a signaltransmitted from the sensor 44 that is disposed immediately before thewindow 13 of the chamber 10A. By this configuration, a laser beam havinga predetermined plane wave can be obtained.

The laser beam that has been corrected by the wave front correction part45 is incident to the reflecting mirror 41 (1) to be reflected, and isincident to the polarization split type isolator 46. The laser beampasses through the isolator 46 and is incident to the reflecting mirror41 (2). The laser beam that has been reflected by the reflecting mirror41 (2) is incident to the window 13 of the chamber 10A via the sensor44.

FIG. 8 is an explanatory diagram showing a configuration of the chamber10A in accordance with the present embodiment. The chamber 10A isclassified roughly into two regions 11 (1) and 11 (2). One region 11 (1)is a light focusing region for arranging a laser beam that is incidentfrom the driver pulse laser light source device 2. The other region 11(2) is an EUV light emission region for generating an EUV light byirradiating a droplet DP with a laser beam.

The two regions 11 (1) and 11 (2) are partitioned by a wall. The lightfocusing region 11 (1) and the EUV light emission region 11 (2) arecommunicated with each other via a small hole that has been formed inthe partition wall that partitions the regions 11 (1) and 11 (2). Apressure in the light focusing region 11 (1) can be specified to beextremely higher than that in the EUV light emission region 11 (2). Bythis configuration, debris that has been generated in the EUV lightemission region 11 (2) can be prevented from intruding into the lightfocusing region 11 (1).

The laser beam that has been incident to the light focusing region 11(1) from the window 13 is reflected by an off-axis parabolic concavemirror 18, and is incident to an off-axis parabolic convex mirror 16(1). The laser beam is provided with a predetermined beam diameter bybeing reflected by the mirrors 18 and 16 (1).

The laser beam that has been specified to have a predetermined beamdiameter is incident to a reflecting mirror 17 to be reflected, and isincident to an off-axis parabolic convex mirror 16 (2). The laser beamthat has been reflected by the off-axis parabolic convex mirror 16 (2)enters the EUV light emission region 11 (2), and irradiates a droplet DPvia a hole part 14A of the EUV light collector mirror 14.

A window that a laser beam pass through, such as windows that theamplifiers 32 (1), 32 (2), 35 (1), and 35 (2) are provided with, windowsthat the SAs 33 (1) and 33 (2) are provided with, and the window 13 ofthe chamber 10A, is preferably formed by a material havingcharacteristics similar to those of a diamond.

A diamond has permeability to a wavelength of 10.6 μm of a CO2 laser andhas a high coefficient of thermal conductivity. Consequently, even inthe case in which a large heat load is applied to a diamond, adistribution of temperature is hard to occur, whereby a shape and anindex of refraction are hard to vary. As a result, for a laser beam thatpasses through a window made of a diamond, a curvature or an angle of awave front of the laser beam are hard to vary.

However, since a diamond is high-priced in general, it may be difficultthat all windows are made of a diamond in the regard of a cost. In thecase in which a cost phase is considered, a window that is used for anelement that a relatively large heat load is applied to is made of adiamond. In the present laser system, a larger heat load is applied toan element that is disposed on a more downstream side. For instance,since a relatively large heat load is applied to the both windows of themain amplifier 35 and the window of the EUV chamber 10A, the windowsshould be made of a diamond. Moreover, since the SA 33 absorbs a CO2laser beam, a large heat load is applied to the SA 33. Consequently, theSA 33 should be made of a diamond regardless of whether the SA 33 isdisposed on an upstream side of a beam or on a downstream side.

A flow of a guide laser beam will be described in the following. Asshown in FIG. 12, the guide laser beam introduction mirror 52 isdisposed between an exit side of the spatial filter 37 and an inlet sideof the first preamplifier 32 (1). The guide laser beam is transmitted toa light path substantially equivalent to that of a driver pulsed laserbeam via the guide laser beam introduction mirror 52.

FIG. 9 is an explanatory diagram schematically showing a principle ofthe wave front correction part 34. FIG. 9( a) shows a case in which aheat load is less, and FIG. 9( b) shows a case in which a heat load islarge. The point of focus in the descriptions of each optical element inthe following is a guide laser beam L3. However, each optical elementalso gives an operation equivalent to that of the guide laser beam to adriver pulsed laser beam.

The wave front correction part 34 is provided with an angle correctionpart 100 and a wave front curvature correction part 200. The anglecorrection part 100 is an optical system that adjusts an angle (adirection of travel) of a laser beam. The wave front curvaturecorrection part 200 is an optical system that adjusts a curvature of awave front of a laser beam (a spread of a beam). The detailedconfiguration example will be described later in another embodiment.

The angle correction part 100 is configured to be provided with, forexample, two reflecting mirrors 101 and 102 that are disposed face toface in parallel. As shown in FIG. 9( b), each of the two reflectingmirrors 101 and 102 is disposed in a rotatable manner around an X axis(an axis perpendicular to FIG. 9) and a Y axis (an axis being at rightangles to the X axis in the same plane) of the reflecting mirror as thecenter of rotation. In other words, each of the two reflecting mirrors101 and 102 is attached in such a manner that a tilt and a rolling canbe carried out.

In the case in which a heat load is less (FIG. 9( a)), since the guidelaser beam L3 travels in accordance with a standard optical axis, it isnot necessary to change an orientation of each of the two reflectingmirrors 101 and 102. In the case in which a heat load is large (FIG. 9(b)), the guide laser beam L3 is incident out of a standard optical axis.Consequently, an orientation of each of the two reflecting mirrors 101and 102 is varied as needed, and an emitting direction of the guidelaser beam L3 is adjusted to correspond to a standard optical axis.

The wave front curvature correction part 200 is configured to beprovided with, for example, a concave mirror 201 and a convex mirror202. By adjusting a relative positional relationship of each of themirrors 201 and 202, a convex face wave and a concave face wave can bemodified to be a plane wave.

FIG. 10 is a block diagram showing an example of a sensor 36. Areflecting mirror 300 on which a coating that reflects the driver pulsedlaser beam L1 and the guide laser beam L3 at a high degree of reflectionis coated is configured to be provided with a beam splitter substrate300A and a holder 300B with a water-cooling jacket for holding the beamsplitter substrate 300A. A reflecting coating that is coated on thereflecting mirror 300 is configured to reflect the driver pulsed laserbeam at a high degree of reflection and to partially reflect the guidelaser beam.

The beam splitter substrate 300A is made of, for example, a materialsuch as silicon (Si), zinc selenide (ZnSe), gallium arsenide (GaAs), anda diamond. Although many of the guide laser beams L3 is reflected by areflecting coating of the beam splitter substrate 300A, a part L3L ofthe guide laser beams L3 is transmitted to the beam splitter substrate300A.

The guide laser beam L3L that has been transmitted to the beam splittersubstrate 300A becomes a sample beam and passes through a band-passfilter BPF to be incident to an optical sensor part 360. The band-passfilter BPF makes a guide laser beam to be transmitted and blocks atransmission of other beams.

As the optical sensor part 360, a sensor such as a beam profiler thatmeasures an intensity distribution of a laser beam, a power sensor thatmeasures a laser duty and a load of an optical element (for instance, acalorimeter and a pyroelectric sensor), and a wave front sensor that cansimultaneously measure a wave front state and a direction of a laserbeam can be used for instance.

FIG. 11 is an explanatory diagram showing a configuration example of anisolator 46. The isolator 46 is configured to be provided with, forexample, a first mirror 461 provided with a heat sink 460, a secondmirror 462, and a third mirror 463. A laser beam that has been reflectedby the third mirror 463 is incident to the light focusing region 11 (1)in which a light focusing optical system is disposed for focusing alaser beam in the chamber 10A via the reflecting mirror 41 (2) and thewindow 13 (see FIG. 8).

The first mirror 461 makes a P polarized light to be transmitted andonly an S polarized light to be reflected by a dielectric multilayerthat has been formed on the surface of the first mirror. For the firstmirror 461, a P polarized light is absorbed into a substrate to becooled by the heat sink 460. A laser beam is incident to the firstmirror 461 as an S polarized light.

A laser beam of an S polarized light that has been reflected by thefirst mirror 461 is incident to the second mirror 462 that is disposedfacing to the first mirror 461 in a diagonal direction. A λ/4 coatingthat generates a phase difference of n/2 is formed on a surface of thesecond mirror 462. Consequently, a laser beam is converted into acircularly polarized light by being reflected by the second mirror 462.

A laser beam of a circularly polarized light is incident to the thirdmirror 463. A coating that reflects a P polarized light and an Spolarized light at a high degree of reflection is coated on the thirdmirror 463. A laser beam that has been reflected by the third mirror 463is focused and irradiated to a droplet DP to generate the plasma PLZ viathe light focusing region 11 (1) in which a light focusing opticalsystem is disposed for focusing a laser beam.

A laser beam that has been reflected by the plasma PLZ returns to alight path equivalent to a light path during an irradiation as acircularly polarized light of a reverse rotation. A return light of acircularly polarized light is reflected by the third mirror 463 and isincident to the second mirror 462. The return light is converted into aP polarized light by being reflected by the λ/4 coating of the secondmirror 462.

A laser light of a P polarized light is incident to the first mirror461. The laser light of a P polarized light that has been incident tothe first mirror 461 is transmitted to the coating of the first mirror461, and is absorbed into a mirror substrate to be converted into aheat. The heat is released by the heat sink 460. Consequently, a laserbeam that is reflected by the plasma PLZ and is returned can beprevented from returning to an inlet side of the isolator 46. By thisconfiguration, a self oscillation caused by a return light of a laserbeam can be prevented.

By using the isolator 46 of the reflecting optical system as shown inFIG. 11, a distortion of a wave front, which occurs for a laser beamthat is transmitted to the isolator 46, can be less as compared with thecase in which an isolator of a transmitting optical system is used.

FIG. 13 is a flowchart of a summary of an operation in accordance withthe present embodiment. As shown in the second embodiment, in the casein which a plurality of wave front correction parts 34 (1) to 34 (4) and45 are disposed, a wave front is corrected in order from a wave frontcorrection part on an upstream side.

At first, the wave front correction controller 60 (1) carries out afirst wave front correction by using the wave front correction part 34(1) that is positioned on the most upstream side (S34), and notifies thelaser controller 70 of that the wave front correction has been completed(S32).

In the next place, after the wave front correction controller 60 (2)confirms that a completion notice has been output from the wave frontcorrection controller 60 (1) of the former stage (S52), the wave frontcorrection controller 60 (2) carries out a second wave front correctionby using the wave front correction part 34 (2) (S56). The wave frontcorrection controller 60 (2) notifies the laser controller 70 of thatthe wave front correction has been completed (S54).

Similarly, after the next wave front correction controller 60 (3)confirms that a completion notice has been sent from the wave frontcorrection controller 60 (2) of the former stage (S62), the wave frontcorrection controller 60 (3) carries out a third wave front correctionby using the wave front correction part 34 (3) (S66). The wave frontcorrection controller 60 (3) notifies the laser controller 70 of thatthe wave front correction has been completed (S64).

Similarly, after the next wave front correction controller 60 (4)confirms that a completion notice has been sent from the wave frontcorrection controller 60 (3) of the former stage (S72), the wave frontcorrection controller 60 (4) carries out a fourth wave front correctionby using the wave front correction part 34 (4) (S76). The wave frontcorrection controller 60 (4) notifies the laser controller 70 of thatthe wave front correction has been completed (S74).

Similarly, after the last wave front correction controller 60 (5)confirms that a completion notice has been sent from the wave frontcorrection controller 60 (4) of the former stage (S82), the wave frontcorrection controller 60 (5) carries out the last wave front correctionby using the wave front correction part 45 (S86). The wave frontcorrection controller 60 (5) notifies the laser controller 70 of thatthe wave front correction has been completed (S84).

The laser controller 70 receives a completion notice for notifying ofthat the wave front correction has been completed in order from each ofthe wave front correction controllers 60 (1) to 60 (5). In the case inwhich the laser controller 70 receives all the completion notices, thelaser controller 70 notifies the EUV light source controller 80 of thatan adjustment of the driver pulse laser light source device 2 has beencompleted.

The present embodiment that is configured as described above has anoperation effect equivalent to that of the first and second embodiments.Moreover, in the present embodiment, the wave front correction parts 34(1) to 34 (4) are corresponded to the amplifiers 32 (1), 32 (2), 35 (1),and 35 (2), respectively, and a laser beam is incident to each amplifierat a suitable curvature and a suitable angle of a wave front.Consequently, a laser beam can be amplified in a more stable manner ascompared with the first and second embodiments.

Embodiment 4

A fourth embodiment of the present invention will be described in thefollowing with reference to FIGS. 14 and 15. In the present embodiment,total four preamplifiers 32 (1) to 32 (4) and total two main amplifiers35 (1) and 35 (2) are included. Moreover, in the present embodiment,only one SA 33 is disposed as compared with the third embodiment. FIG.14 shows the case in which a driver pulsed laser beam and a guide laserbeam are output. FIG. 15 shows the case in which only a guide laser beamis output.

The present embodiment is configured to be provided with a spatialfilter 37, a relay optical system 31 (1), a preamplifier 32 (1), a relayoptical system 31 (2), a preamplifier 32 (2), an SA 33, a relay opticalsystem 31 (3), a preamplifier 32 (3), a relay optical system 31 (4), apreamplifier 32 (4), a relay optical system 31 (5), a guide laser beamintroduction mirror 52, a reflecting mirror 38, a wave front correctionpart 34 (1), a main amplifier 35 (1), a sensor 36 (1), a wave frontcorrection part 34 (2), a main amplifier 35 (2), a sensor 36 (2), a wavefront correction part 45, a reflecting mirror 41 (1), an isolator 46(also possible to be removed), a reflecting mirror 41 (2), and a sensor44 in order from the upstream side.

The guide laser beam introduction mirror 52 is disposed at a turn-aroundsection of a light path between the preamplifier 34 (4) and the mainamplifier 35 (1). It should be noted that the guide laser beamintroduction mirror 52 shown in FIGS. 14 and 15 is configured as a firsttype guide laser beam introduction mirror that makes the guide laserbeam be transmitted and that makes the driver pulsed laser beam bereflected.

The driver pulsed laser beam is transmitted to the total fourpreamplifiers 32 (1) to 32 (4) to be amplified to a value of a certaindegree. If a driver pulsed laser beam having a relatively high outputpower is transmitted to the guide laser beam introduction mirror 52, aheat load that is applied to the guide laser beam introduction mirror 52is large, whereby a distortion or the like occurs in the guide laserbeam introduction mirror 52. On the other hand, in the case in which aguide laser beam introduction mirror is configured in such a manner thata driver pulsed laser beam is reflected and a guide laser beam istransmitted like the present embodiment, a heat load that is applied tothe guide laser beam introduction mirror 52 can be suppressed.

The wave front correction part 34 (1) corrects a laser beam that passesthrough the main amplifier 35 (1). The wave front correction part 34 (2)corrects a laser beam that passes through the main amplifier 35 (2).FIG. 15 is a block diagram showing the state in which only a guide laserbeam is output.

In the present embodiment that is configured as described above, anoptical performance of a laser beam is corrected in order from a wavefront correction part on an upstream side like the third embodiment. Thepresent embodiment also has an operation effect equivalent to that ofthe third embodiment.

Embodiment 5

A fifth embodiment of the present invention will be described in thefollowing with reference to FIGS. 16 to 18. In the present embodiment,some examples that introduce a guide laser beam to a light path of adriver pulsed laser beam will be described.

A coating 521 that transmits a guide laser beam L3 and that reflects adriver pulsed laser beam L1 is coated on the surface of the guide laserbeam introduction mirror 52 shown in FIG. 16( a). The driver pulsedlaser beam L1 that has been reflected by a reflecting mirror 54 is alsoreflected by the coating 521 of the guide laser beam introduction mirror52, and travels toward the right side in the figure.

For instance, the guide laser beam L3 that has been output from theguide laser device 50 that is configured as a helium neon laser lightsource that oscillates in a single transverse mode is incident to alaser collimator 51, whereby a beam diameter and a wave front shape ofthe guide laser beam L3 are adjusted.

The laser collimator 51 is configured to be provided with, for example,two convex lenses 511 and 512 and a spatial filter 513 that is disposedbetween the convex lenses. A rear side focus F1 of the first convex lens511 and a front side focus F2 of the second convex lens 512 arecorresponded to each other, and the spatial filter 513 is disposed atthe corresponded position of F1 and F2.

By the above configuration, as shown in FIG. 16( b), only the guidelaser beam in a single transverse mode is transmitted to the spatialfilter 513 and is incident to the second convex lens 512. By the secondconvex lens 512, a beam diameter of the guide laser beam is expanded tobe substantially equivalent to a beam diameter of a driver pulsed laserbeam. The guide laser beam having a beam diameter substantiallyequivalent to that of a driver pulsed laser beam travels on a light pathsubstantially equivalent to that of a driver pulsed laser beam. In otherwords, the guide laser beam introduction mirror 52 plays a role ofsuperimposing the guide laser beam to the driver pulsed laser beam.

FIG. 17 is an explanatory diagram showing another example forintroducing a guide laser beam. A coating 521A that transmits a driverpulsed laser beam L1 and that reflects a guide laser beam L3 is coatedon the surface of the guide laser beam introduction mirror 52A shown inFIG. 17.

The guide laser beam L3 that has been output from a guide laser device50 is focused by a light focusing lens 511A, and is incident to a singlemode fiber 513A. The output part of the single mode fiber 513A isdisposed at a front side focus position of a collimator lens 512A asshown in FIG. 17( b).

A guide laser beam that has been transmitted to the single mode fiber513A spreads at a predetermined angle and is incident to the collimatorlens 512A to be converted into a plane wave by the collimator lens 512A.The guide laser beam that has been converted into a plane wave is highlyreflected by the coating 521A of the guide laser beam introductionmirror 52A. By this configuration, the driver pulsed laser beam and theguide laser beam are provided with an almost equivalent beam and analmost equivalent optical axis. In the case of an example shown in FIG.17, since the single mode optical fiber 513A is used, an alignment iseasy to be carried out.

FIG. 18 is an explanatory diagram showing furthermore another examplefor introducing a guide laser beam. In an example shown in FIG. 18, aconfiguration that outputs a driver pulsed laser beam and aconfiguration that introduces a guide laser beam into a light path of adriver pulsed laser beam are coupled with each other.

The driver laser oscillator 20 is configured to be provided with, forexample, a laser chamber 21 provided with a window 26, a rear mirror 22disposed on one side of the laser chamber 21 and apart from the laserchamber 21, a plane output mirror 23 disposed on the other side of thelaser chamber 21 and apart from the laser chamber 21, and pinholes 24and 25 disposed between the window 26 and the mirrors 22 and 23,respectively. The pinhole 24 restricts a spatial transverse mode of adriver pulsed laser beam.

A guide laser device 50 is disposed on one side of the rear mirror 22. Acorrection lens 511B is disposed between the guide laser device 50 andthe rear mirror 22. After a guide laser beam is focused by thecorrection lens 511B, the guide laser beam is incident to the rearmirror 22 that has been formed in a concave face shape.

A coating that is configured to reflect the driver pulsed laser beam ata high degree of reflection and to transmit the guide laser beam isformed on the rear mirror 22. Consequently, as shown in FIG. 18( b), theguide laser beam is transmitted to the rear mirror 22, and in incidentto the laser chamber 21 via the pinhole 24 and the window 26. Here, therear mirror 22 is operated as a concave lens to convert the guide laserbeam into a plane wave.

The guide laser beam passes through the pinhole 24, the window 26 on therear side, the laser chamber 21, the window 26 on the front side, andthe pinhole 25, and is incident to the plane output mirror (OC) 23. Acoating that is configured to reflect a part of the driver pulsed laserbeam and to transmit the guide laser beam is formed on the plane outputmirror 23.

The guide laser beam that has been transmitted to the plane outputmirror 23 travels on a light path equivalent to that of the driverpulsed laser beam. By configuring each optical element disposed on thedownstream side of the driver laser oscillator 20 as a reflection typeoptical element, an optical axis of the driver pulsed laser beam and anoptical axis of the guide laser beam can be prevented from being out ofalignment from each other. This is because a chromatic aberration doesnot occur for the reflecting optical system. Consequently, it ispreferable for instance that a spatial filter (a combination of twooff-axis parabolic mirrors), a relay optical system, a wave frontcorrection part and others are configured as a reflection type device.Since the windows 13 and 26 cannot be configured in a reflection type,the windows 13 and 26 are configured in a transmission type.

As an optical element for introducing a guide laser beam, an opticalelement made of a diamond is preferably used. This is because a diamondhas an excellent thermal conductivity and can suppress a distribution oftemperature from occurring. Consequently, the rear mirror 22 and theplane output mirror 23 should be fabricated by using a diamondsubstrate.

Embodiment 6

A sixth embodiment of the present invention will be described in thefollowing with reference to FIGS. 19 to 20. In the present embodiment, amodification example of a positional relationship of a wave frontcorrection part 34, a sensor 36, and the wave front variation generatingparts (32, 33, and 35) will be described. A wave front correction partincludes a wave front correction part 34 in an amplifying process and awave front correction part 45 in a light focusing process. The wavefront correction part 34 will be described as a representative in thefollowing explanation.

As a wave front variation generating part that can generate a variationin a wave front due to a heat load, there can be mentioned for instancea preamplifier 32, a main amplifier 35, an SA 33, a relay optical system31, a reflecting mirror, a polarization element, a retarder, and otheroptical elements of many kinds. Here, as a matter of practicalconvenience for an explanation, a preamplifier 32, a main amplifier 35,and an SA 33 will be described in large part as an example for a wavefront variation generating part.

FIG. 19( a) shows a configuration in which a wave front correction part34 is disposed on the upstream side of the wave front variationgenerating parts 32, 33, and 35 and a sensor 36 is disposed on thedownstream side of the wave front variation generating parts 32, 33, and35. After the laser beam L1 and the guide laser beam L3 are corrected bythe wave front correction part 34, the laser beam L1 and the guide laserbeam L3 are input to the sensor 36. The wave front correction controller60 controls the wave front correction part 34 in such a manner that anoptical performance of a laser beam (a curvature or an angle of a wavefront) that is measured by the sensor 36 is in a predetermined value.

FIG. 19( b) shows a configuration in which a wave front correction part34 and a sensor 36 are disposed on the downstream side of the wave frontvariation generating parts 32, 33, and 35. The wave front correctionpart 34 is disposed between the wave front variation generating parts32, 33, and 35 and the sensor 36.

After the laser beam L1 and the guide laser beam L3 pass through a relayoptical system 31 and the wave front variation generating parts 32, 33,and 35, the laser beam L1 and the guide laser beam L3 are incident tothe wave front correction part 34. The wave front correction controller60 controls the wave front correction part 34 in such a manner that anoptical performance that is detected by the sensor 36 is in apredetermined value.

FIG. 19( c) shows a configuration in which a sensor 36 and the wavefront variation generating parts 32, 33, and 35 are disposed on thedownstream side of a wave front correction part 34. The sensor 36 isdisposed between the wave front correction part 34 and the wave frontvariation generating parts 32, 33, and 35. The wave front correctioncontroller 60 controls the wave front correction part 34 in such amanner that an optical performance of a laser beam that is detected bythe sensor 36 is in a predetermined value.

In FIG. 19( c), the wave front correction controller 60 controls thewave front correction part 34 in such a manner that an opticalperformance that is detected by the sensor 36 in the case in which anormal wave front is recovered when a laser beam is transmitted to thewave front correction part 34 and the wave front variation generatingparts 32, 33, and 35 using a distortion of a wave front that may occurin the wave front variation generating parts 32, 33, and 35 as a knownone is in a predetermined value.

As shown in FIG. 20, a plurality of wave front correction parts 34 or aplurality of sensors 36 can also be disposed. As shown in FIG. 20( a),the sensors 36 (1) and 36 (2) are disposed on an upstream side and adownstream side, respectively, of the wave front variation generatingparts 32, 33, and 35, and a wave front correction part 34 is disposed onthe most upstream side.

The wave front correction controller 60 controls the wave frontcorrection part 34 in such a manner that a predetermined opticalperformance that can be measured in each of the sensors 36 (1) and 36(2) based on an optical performance of a laser beam that is detected bythe sensor 36 (1) and an optical performance of a laser beam that isdetected by the sensor 36 (2).

In FIG. 20( b), the wave front correction part 34 and the sensors 36 aredisposed on an upstream side and a downstream side of the wave frontvariation generating parts 32, 33, and 35. The wave front correctionpart 34 (1) and the sensor 36 (1) are disposed on an upstream side ofthe wave front variation generating parts 32, 33, and 35. The wave frontcorrection part 34 (2) and the sensor 36 (2) are disposed on adownstream side of the wave front variation generating parts 32, 33, and35.

After the laser beam L1 and the guide laser beam L3 that have passedthrough the sensor 36 (1) are transmitted to the wave front variationgenerating parts 32, 33, and 35, the laser beam L1 and the guide laserbeam L3 are input to the wave front correction part 34 (2). The laserbeam L1 and the guide laser beam L3 are then transmitted to the wavefront correction part 34 (2) and are input to the sensor 36 (2). Thewave front correction controller 60 controls the wave front correctionparts 34 (1) and 34 (2) in such a manner that a laser beamcharacteristic that is measured at the respective position of thesensors 36 (1) and 36 (2) is a predetermined characteristic at therespective position.

Embodiment 7

A seventh embodiment of the present invention will be described in thefollowing with reference to FIG. 21. In the present embodiment, anexample of a wave front curvature correction part 200A that isconfigured as a reflection type optical system will be described. Thewave front curvature correction part 200A is configured to be providedwith two reflecting mirrors 205 (1) and 205 (2) and two off-axisparabolic concave mirrors 206 (1) and 206 (2). The reflecting mirror 205(1) and the off-axis parabolic concave mirror 206 (1) that arepositioned on upper side in FIG. 21 are attached to a plate 207. Theplate 207 can be moved in a vertical direction in FIG. 21. Thereflecting mirror 205 (1) and the off-axis parabolic concave mirror 206(1) can also be moved in a vertical direction together with the plate207.

FIG. 21( a) shows an arrangement in the case in which the laser beam L1and the guide laser beam L3 that have been input as a parallel light (aplane wave) are output as they are parallel lights (plane waves). Inthis case, a focus position of the off-axis parabolic concave mirror 206(1) and a focus position of the off-axis parabolic concave mirror 206(2) are corresponded to each other to be in a state of a confocal cf.

The laser beam L1 and the guide laser beam L3 are incident to thereflecting mirror 205 (2) from a left side (an upstream side) in FIG. 21to be reflected, and are incident to the other reflecting mirror 205(1). The laser beam L1 and the guide laser beam L3 that have beenreflected by the reflecting mirror 205 (1) are then incident to theoff-axis parabolic concave mirror 206 (1).

The laser beam L1 and the guide laser beam L3 are reflected by theoff-axis parabolic concave mirror 206 (1) at a reflecting angle of 45degrees, and are focused into a focus position cf. The laser beamsspread from the focus position cf, and are incident to the off-axisparabolic concave mirror 206 (2) to be reflected at a reflecting angleof 45 degrees.

FIG. 21( b) shows an arrangement in the case in which the laser beam L1and the guide laser beam L3 that have been input as a converging light(a concave wave front) are converted into a parallel light (a planewave) to be output. In this case, the laser beam L1 and the guide laserbeam L3 are focused at a position of a light focusing point f on a frontside of the focus position cf of the off-axis parabolic concave mirror206 (1). By moving the plate 207 downward, the position of a lightfocusing point f is moved to a downstream side on an optical axis. Bythis configuration, the position of a light focusing point f of theoff-axis parabolic concave mirror 206 (1) and the focus position of theoff-axis parabolic concave mirror 206 (2) are corresponded to each otheron an optical axis.

In the case in which the laser beam L1 and the guide laser beam L3 areinput as a diverging light (a convex wave front), the plate 207 is movedupward in FIG. 21.

For the wave front curvature correction part 200A that is configured asdescribed above, the reflecting mirror 205 (1) and the off-axisparabolic concave mirror 206 (1) are fixed to a plate 207, and thereflecting mirror 205 (1) and the off-axis parabolic concave mirror 206(1) are moved simultaneously on an optical axis (in a vertical directionin FIG. 21). By this configuration, in the present embodiment, anoptical axis of an input light and an optical axis of an output lightare corresponded to each other, whereby a curvature of a wave front canbe corrected.

Moreover, since the wave front curvature correction part 200A inaccordance with the present embodiment is configured as a reflectiontype optical system, even in the case in which the laser beam L1 and theguide laser beam L3 pass through the wave front curvature correctionpart 200A, a wave front variation caused by a heat can be less. By thisconfiguration, even in the case in which a laser beam of a high outputpower is used, a curvature of a wave front can be corrected with a highdegree of accuracy.

Embodiment 8

An eighth embodiment of the present invention will be described in thefollowing with reference to FIG. 22. A wave front curvature correctionpart 200B in accordance with the present embodiment is configured by areflection type optical system that includes an off-axis parabolicconcave mirror 206, an off-axis parabolic convex mirror 208, and tworeflecting mirrors 205 (1) and 205 (2).

The off-axis parabolic concave mirror 206 and the reflecting mirror 205(1) are attached to a plate 207 that can be moved in a verticaldirection. Moreover, a focus position of the off-axis parabolic convexmirror 208 and a focus position of the off-axis parabolic concave mirror206 are arranged to be corresponded to each other at a confocal cf.

The laser beam L1 and the guide laser beam L3 that have a parallel wavefront are reflected by the off-axis parabolic convex mirror 208, and areincident to the off-axis parabolic concave mirror 206 as a diverginglight to be converted into a plane wave. The laser beams of a plane waveare reflected by the reflecting mirrors 205 (1) and 205 (2) to beoutput. Similarly to the seventh embodiment, the wave fronts of thelaser beam L1 and the guide laser beam L3 are corrected to be a planewave by moving the plate 207 in a vertical direction, and the laser beamL1 and the guide laser beam L3 are output.

The present embodiment that is configured as described above has anoperation effect equivalent to that of the seventh embodiment. Moreover,in the present embodiment, by combining a concave face of the off-axisparabolic concave mirror 206 and a convex face of the off-axis parabolicconvex mirror 208, a distance between both the off-axis parabolicmirrors can be shortened. Consequently, the total dimensions can beminiaturized as compared with the seventh embodiment.

Embodiment 9

A ninth embodiment of the present invention will be described in thefollowing with reference to FIGS. 23 and 24. In the present embodiment,the wave front curvature correction parts 200C and 200D are configuredby an arrangement of a convex mirror 209 and a concave mirror 210 in a Zpattern.

FIG. 23 shows the wave front curvature correction part 200C that isconfigured by an arrangement of a spherical convex mirror 209 on anupstream side and a spherical concave mirror 210 on a downstream side ina Z pattern. For instance, in the case in which the laser beam L1 andthe guide laser beam L3 that are a diverging light (a convex wave front)are incident to the convex mirror 209, the convex mirror 209 reflectsthe laser beam L1 and the guide laser beam L3 at a small incident angleα of 3 degrees or less. The laser beam L1 and the guide laser beam L3that have been reflected are incident to the concave mirror 210 at anincident angle α, and are converted into a parallel light (a plane wave)to be output.

For instance, by moving a position of the concave mirror 210 along areflecting optical axis of the convex mirror 209 as shown by an arrow inFIG. 23, a wave front of a laser beam can be converted into a planewave.

FIG. 24 shows the wave front curvature correction part 200D that isconfigured by an arrangement of a spherical concave mirror 210 on anupstream side and a spherical convex mirror 209 on a downstream side ina Z pattern. For instance, in the case in which the laser beam L1 andthe guide laser beam L3 that are a diverging light (a convex wave front)are incident to the concave mirror 210, the concave mirror 210 reflectsthe laser beam L1 and the guide laser beam L3 at a small incident angleα (for instance, 3 degrees or less). The laser beam L1 and the guidelaser beam L3 that have been reflected are incident to the convex mirror209 at an incident angle α, and are converted into a parallel light (aplane wave). For instance, by moving a position of the convex mirror 209along a reflecting optical axis of the concave mirror 210 as shown by anarrow in FIG. 24, a curvature of a wave front of the laser beam L1 andthe guide laser beam L3 can be converted into that of a plane wave.

In the present embodiment as described above, since the wave frontcurvature correction part can be configured by the convex mirror 209 andthe concave mirror 210, a production cost can be reduced. Moreover,since the present configuration is a reflecting optical system, a wavefront variation that occurs in the case in which the laser beam L1 andthe guide laser beam L3 pass through the wave front curvature correctionpart can also be reduced.

In the present embodiment, an optical axis of the laser beam L1 and theguide laser beam L3 that are output are moved in parallel from anoptical axis of the laser beam L1 and the guide laser beam L3 that havebeen input. Consequently, an optical system that makes an optical axisof an output light correspond to an optical axis of an input light canalso be configured additionally.

Embodiment 10

A tenth embodiment of the present invention will be described in thefollowing with reference to FIGS. 25 and 26. The present embodiment usesa variable mirror in which a curvature of a reflecting face of thevariable mirror can be controlled in a variable manner by a controlsignal that is transmitted from a wave front correction controller 60.In the present embodiment, such a variable mirror is referred to as aVRWM (Variable Radius Wave front Mirror).

The wave front curvature correction part 200E in accordance with thepresent embodiment is configured by the VRWM. FIGS. 25( a) and 26(a)show the case in which the laser beam L1 and the guide laser beam L3that are incident as a plane wave (a parallel light) are emitted as aplane wave (a parallel light). In the case in which a plane wave isconverted into a plane wave, a surface of the VRWM is controlled to beflat.

FIG. 25( b) shows the case in which the laser beam L1 and the guidelaser beam L3 that have a convex wave front (a diverging light) areconverted into a laser beam of a plane wave (a parallel light). In thiscase, a shape of the VRWM is controlled in such a manner that the VRWMhas a concave face.

FIG. 25( c) shows the case in which the laser beam L1 and the guidelaser beam L3 that have a concave wave front (a converging light) areconverted into a laser beam of a plane wave (a parallel light). In thiscase, a shape of the VRWM is controlled in such a manner that the VRWMhas a convex face.

FIG. 26( b) shows the case in which a plane wave is converted into aspherical wave of a concave wave front. To convert a plane wave into aspherical wave of a concave wave front, a surface of the VRWM iscontrolled to be in a toroidal form of a concave face (in the case inwhich an incident angle is approximately 45 degrees). By thisconfiguration, a laser beam that has been reflected by the VRWM isfocused into a focal distance F. A spherical wave immediately afterbeing reflected the surface of the VRWM in a toroidal form is aspherical wave of a concave wave front having a curvature radius R. Thefocal distance F is equivalent to a curvature radius R of the sphericalwave.

FIG. 26( c) shows the case in which a plane wave is converted into aspherical wave of a convex wave front. To convert a plane wave into aspherical wave of a convex wave front, a surface of the VRWM iscontrolled to be in a toroidal form of a convex face (in the case inwhich an incident angle is approximately 45 degrees). By thisconfiguration, a convex face wave that has been reflected by the VRWM isa wave front that is emitted from a point light source of a position ofa focal distance −F. A spherical wave immediately after being reflectedthe surface of the VRWM in a toroidal form is a spherical wave having acurvature radius −R. The focal distance −F is equivalent to a curvatureradius −R of a wave front.

In the present embodiment that is configured as described above, sincethe wave front curvature correction part 200E can be configured by onlythe VRWM, the number of components can be reduced and the wave frontcurvature correction part 200E can be compactly formed. In addition,only one reflection enables a correction, thereby improving anefficiency of a correction.

Moreover, for the wave front curvature correction part 200E inaccordance with the present embodiment, an optical axis of the laserbeam L1 and the guide laser beam L3 that are incident can be varied atan angle of 45 degrees for an emission. Consequently, in the case inwhich the wave front curvature correction part 200E is used at theposition in which a light path of the laser beam L1 and the guide laserbeam L3 is varied at an angle of 45 degrees, a reflecting mirror 41 thatreflects the beams at an angle of 45 degrees can be omitted. By thisconfiguration, the structure of the present embodiment can be simplifiedand a production cost can be reduced.

Embodiment 11

An eleventh embodiment of the present invention will be described in thefollowing with reference to FIG. 27. In the present embodiment, the wavefront curvature correction part 200F is configured by an arrangement ofa VRWM 213 and a reflecting mirror 214 in a Z pattern.

As shown in FIG. 27( a), in the case in which the laser beam L1 and theguide laser beam L3 that are incident to the VRWM as a plane wave areemitted as a plane wave, a surface of the VRWM 213 is controlled to bein a flat shape. As shown in FIG. 27( b), in the case in which the laserbeam L1 and the guide laser beam L3 that are incident to the VRWM as aconvex face wave are converted into a plane wave, a shape of the VRWM213 is specified to be in a spherical shape of a concave face. As shownin FIG. 27( c), in the case in which the laser beam L1 and the guidelaser beam L3 that are incident to the VRWM as a concave face wave areconverted into a plane wave, a shape of the VRWM 213 is specified to bein a spherical shape of a convex face.

The present embodiment that is configured as described above has anoperation effect equivalent to that of the ninth embodiment. However, anincident optical axis and an outgoing optical axis of the laser beam L1and the guide laser beam L3 are out of alignment in parallel from eachother and are not corresponded to each other. Consequently, an opticalsystem that makes an optical axis of an output light correspond to anoptical axis of an input light can also be configured additionally.

Embodiment 12

A twelfth embodiment of the present invention will be described in thefollowing with reference to FIG. 28. In the present embodiment, the wavefront correction part 34A in which an angle correction part and a wavefront curvature correction part can be used together with each other.The wave front correction part 34A is configured to be provided with bya VRWM 110 and a reflecting mirror 111.

FIG. 28( a) shows a case in which a heat load is less. The laser beam L1and the guide laser beam L3 as a plane wave are incident to andreflected by the reflecting mirror 111 at an angle of 45 degrees, andare incident to the VRWM 110 at an incident angle of 45 degrees. TheVRWM 110 is controlled to be in a flat shape. The laser beam L1 and theguide laser beam L3 are reflected by a flat mirror face of the VRWM 110,and are output in a state of a plane wave.

The present invention is not limited to the case in which an incidentlight of a plane wave is converted into an outgoing light of a planewave. For instance, in such a manner that a laser beam that is input asa diverging light (a convex wave front) is output as the laser beam L1and the guide laser beam L3 that are provided with a wave front of adesired curvature, a focal distance of the VRWM can be controlled to bea constant value.

FIG. 28( b) shows a case in which an angle (a direction) and a curvatureof a wave front for the laser beam L1 and the guide laser beam L3 arevaried. A direction of a wave front for the laser beam L1 and the guidelaser beam L3 that are incident is tilted downward in FIG. 28 due to aninfluence of a heat load, and a wave front of the laser beam L1 and theguide laser beam L3 is varied to a diverging light (a convex wavefront). In this case, an angle of the reflecting mirror 111 iscontrolled in such a manner that an optical axis of the laser beam L1and the guide laser beam L3 that are reflected by the reflecting mirror111 is corresponded to a standard optical axis.

The laser beam L1 and the guide laser beam L3 that are reflected by thereflecting mirror 111 are incident to the VRWM 110 at an incident angleof 45 degrees. In such a manner that the laser beam L1 and the guidelaser beam L3 that are reflected by the VRWM 110 become a plane wave, ashape of the VRWM 110 is specified to be a concave face shape.

The case in which the laser beam L1 and the guide laser beam L3 as aconvex face wave are converted into a plane wave has been describedabove. However, the present invention is not limited to the case. Thelaser beam L1 and the guide laser beam L3 as a concave face wave canalso be converted into a plane wave, and an incident light as a convexface wave or a concave face wave can be converted into an outgoing lightprovided with a wave front of a desired curvature.

In the case of an incident angle within a permissible aberration, anoptical axis of an outgoing light can be corresponded to a standardoptical axis by controlling an angle of the two axes in a horizontaldirection and in a vertical direction of the VRWM 110 (by controlling atilt and a rolling) for instance.

Embodiment 13

A thirteenth embodiment of the present invention will be described inthe following with reference to FIG. 29. In the present embodiment, thewave front correction part 34B in which an angle correction part and awave front curvature correction part can be used together with eachother is configured by an arrangement of a reflecting mirror 113 and aVRWM 112 in a Z pattern. An incident angle is 2.5 degrees.

FIG. 29( a) shows a case in which a heat load is low. The laser beam L1and the guide laser beam L3 as a plane wave are incident to andreflected by the reflecting mirror 113 at an incident angle of 2.5degrees. The laser beam L1 and the guide laser beam L3 that have beenreflected are incident to the VRWM 112 at an incident angle of 2.5degrees. A shape of the VRWM 112 is controlled to be a flat shape. Thelaser beam L1 and the guide laser beam L3 are reflected in a state of aplane wave. Although the case of a plane wave has been described above,the present invention is not limited to the case. For instance, even inthe case in which a convex face wave or a concave face wave is input,the convex face wave or the concave face can be output as the laser beamL1 and the guide laser beam L3 that is provided with a wave front of apredetermined curvature by varying a shape of the VRWM 112.

FIG. 29( b) shows a case in which a heat load is high. The followingdescribes the case in which an angle of the laser beam L1 and the guidelaser beam L3 that are incident is tilted downward in FIG. 29 and a wavefront of the laser beam L1 and the guide laser beam L3 becomes a concaveface. In this case, an angle of the reflecting mirror 113 is changed insuch a manner that an optical axis of the laser beam L1 and the guidelaser beam L3 that are reflected by the reflecting mirror 113 iscorresponded to a standard optical axis (an optical axis shown in FIG.29( a)).

The laser beam L1 and the guide laser beam L3 that have been reflectedby the reflecting mirror 113 are incident to the VRWM 112 at an incidentangle of 2.5 degrees. In such a manner that the laser beam L1 and theguide laser beam L3 that are reflected by the VRWM 112 become a planewave, a shape of the VRWM 112 is changed to be a convex face shape andan angle thereof is adjusted. The present invention is not limited tothe case of a conversion into a plane wave. A concave face and a convexface wave can also be converted into a wave front of desired curvature.This can be applied to the embodiments that will be described in thefollowing.

Embodiment 14

A fourteenth embodiment of the present invention will be described inthe following with reference to FIG. 30. In the present embodiment, thewave front correction part 34C in which an angle correction part and awave front curvature correction part can be used together with eachother is configured by using a deformable mirror 120 and a reflectingmirror 121.

As shown in FIG. 30, the deformable mirror 120 and the reflecting mirror121 are arranged in a Z pattern. A shape of a reflecting face of thedeformable mirror 120 can be controlled in a variable manner accordingto a control signal that is transmitted from a wave front correctioncontroller 60.

In the case in which a laser beam of a distorted wave front is incidentto the deformable mirror 120, a shape of a reflecting face of thedeformable mirror 120 is adjusted in accordance with the incident wavefront. The deformable mirror 120 corrects a wave front of the incidentlaser beam L1 and the incident guide laser beam L3 to be a plane wave,and reflects the laser beam L1 and the guide laser beam L3. The laserbeam L1 and the guide laser beam L3 that have been corrected to be aplane wave are reflected by the reflecting mirror 121 to be output.

By using the deformable mirror 120, a wave front that is not a sphericalwave, such as a wave front in an S shape, can also be converted into aplane wave or a desired spherical wave. Moreover, a direction of thelaser beam L1 and the guide laser beam L3 can also be corrected for asmall angle. Furthermore, by controlling a tilt and a rolling for thereflecting mirror 121 and the deformable mirror 120, a direction of thelaser beam L1 and the guide laser beam L3 can also be adjusted. This canbe applied to an embodiment 15 that will be described in the following.

Embodiment 15

A fifteenth embodiment of the present invention will be described in thefollowing with reference to FIG. 31. In the present embodiment, the wavefront correction part 34D is configured by coupling a deformable mirror120 with a polarization control. The wave front correction part 34D isconfigured to be provided with a deformable mirror 120, a beam splitter122, and a λ/4 substrate 123 that shifts a phase by 90 degrees to theboth wavelengths of the laser beam L1 and the guide laser beam L3. Thewave front variation generating parts 32, 33, and 35 can be disposedbetween the beam splitter 122 and the λ/4 substrate 123.

For instance, a laser beam of a P polarized light (a wave front ofpolarization including a plane of the paper) is incident to the beamsplitter 122 on which a coating that separates a P polarized light andan S polarized light to the both wavelengths of the laser beam L1 andthe guide laser beam L3 has been formed. A wave front of the laser beamL1 and the guide laser beam L3 is input to the beam splitter 122 in astate of a plane wave. However, a wave front of the laser beam L1 andthe guide laser beam L3 is distorted in an S shape since the laser beamL1 and the guide laser beam L3 pass through the wave front variationgenerating parts 32, 33, and 35 from the beam splitter 122.

The laser beam L1 and the guide laser beam L3 that have passed throughthe wave front variation generating parts 32, 33, and 35 are transmittedto the λ/4 substrate 123 to be a circularly polarized light. The wavefront that has been distorted in an S shape is corrected to apredetermined wave front by the deformable mirror 120 that has beenadjusted to be in a suitable shape.

The laser beam L1 and the guide laser beam L3 in which the wave frontthereof has been corrected are transmitted to the λ/4 substrate 123again to be converted into an S polarized light. The laser beam L1 andthe guide laser beam L3 of an S polarized light are transmitted to thewave front variation generating parts 32, 33, and 35 to be convertedfrom a predetermined wave front into a plane wave. The laser beam L1 andthe guide laser beam L3 that have been converted into a plane wave areincident to the beam splitter 122.

The laser beam L1 and the guide laser beam L3 of an S polarized lightare reflected by the beam splitter 122 to be output as a plane wave. Byadjusting a shape of a surface of the deformable mirror 120, the laserbeam L1 and the guide laser beam L3 can be output in a shape of a wavefront other than a plane wave.

Embodiment 16

A sixteenth embodiment of the present invention will be described in thefollowing with reference to FIG. 32. In the present embodiment, a sensor36A is configured by using a diffraction type mirror 301. A grating 301Ais formed on the surface of the diffraction type mirror 301. Moreover,the diffraction type mirror 301 is provided with a cooling water flowpath 301B in which a cooling water flows.

The diffraction type mirror 301 reflects an incident laser beam at anangle of 45 degrees. The reflecting light is a zero order light and hasthe highest intensity. The zero order light can highly reflect the laserbeam L1 and the guide laser beam L3. A −(minus) 1st order light that isobtained by a diffraction of the guide laser beam L3 has a lowintensity. An optical sensor part 360 receives the −(minus) 1st orderlight and measures the characteristics of the laser beam. Although theguide laser beam L3−(minus) 1st order light is a sample light in thepresent embodiment, lights of other orders other than a 0th order lightcan also be detected.

Embodiment 17

A seventeenth embodiment of the present invention will be described inthe following with reference to FIG. 33. In the present embodiment, asensor 36B is configured by using a window 300W. The window 300W isconfigured to be provided with a window substrate 300AW and a holder300BW that holds the window substrate 300AW. The holder 300BW isconfigured to be provided with a cooling water jacket, which is notshown.

The window 300W is disposed in a tilted state to a certain degree on anoptical axis of a driver pulse laser. A slight laser beam L1 and aslight guide laser beam L3 that have been reflected by the surface ofthe window 300W are incident to the optical sensor part 360 as a samplelight.

As the window 300W, a window of the amplifiers 32 and 35 and the window13 of the EUV chamber 10 can also be used for instance. In this case, itis not necessary to dispose a window only for obtaining a sample lightfor a measurement, thereby reducing a production cost. The windowsubstrate 300AW is made of a material, such as a diamond, having anexcellent thermal conductivity for transmitting a CO2 laser beam.

For the parallel plane window 300W, a laser beam is reflected slightlyon both of the surface and the rear face, and is incident to the opticalsensor part 360 as a sample light. Consequently, the laser beam is notsuitable for a measurement of a beam profile. However, a sample lightcan be focused into a focus position by using a light focusing lens, anda position of a focal image can be measured, whereby a direction of alaser beam can be measured. Moreover, in the case in which the driverpulsed laser beam L1L is measured, a duty of a beam line and a power forthe laser can also be measured without inconvenience.

Embodiment 18

An eighteenth embodiment of the present invention will be described inthe following with reference to FIG. 34. In the present embodiment, asensor 36C is configured by using the beam profilers 304A and 304B. Thebeam profiler 304A detects a transmitted light of a reflecting mirror302A, and the beam profiler 304B detects a transmitted light of areflecting mirror 302B. An angle of the reflecting mirror 302A isadjusted according to a measured result of the beam profiler.

A lens 303A is disposed between the rear face side of the reflectingmirror 302A and the beam profiler 304A. Similarly, a lens 303B isdisposed between the rear face side of the reflecting mirror 302B andthe beam profiler 304B.

In the case in which the laser beam L1 and the guide laser beam L3 of aplane wave is transmitted to a relay optical system 31 and the wavefront variation generating parts 32, 33, and 35, a direction of thelaser beam and a curvature of a wave front are varied. The laser beam L1and the guide laser beam L3 in which a direction of the laser beams anda curvature of a wave front have been varied are incident to the wavefront correction part 34. The wave front correction part 34 corrects acurvature of a wave front and a direction of the laser beam L1 and theguide laser beam L3, and outputs the laser beam L1 and the guide laserbeam L3.

The laser beam L1 and the guide laser beam L3 that have been correctedby the wave front correction part 34 are reflected by the reflectingmirror 302A and are incident to the reflecting mirror 302B. On the otherhand, a sample light L3L that is slightly transmitted to the reflectingmirror 302A is transcribed on a two-dimensional sensor that is includedin the beam profiler 304A by a transcription lens 303A. A beam shape anda position of the guide laser beam L3 are measured by thetwo-dimensional sensor.

The data that has been measured by the beam profiler 304A is input tothe wave front correction controller 60. The wave front correctioncontroller 60 transmits a control signal to the wave front correctionpart 34 to control the wave front correction part 34 in such a mannerthat a position of the guide laser beam is set to be a standardposition.

On the other hand, the guide laser beam L3L that has been slightlytransmitted to the reflecting mirror 302B is transcribed on atwo-dimensional sensor that is included in the beam profiler 304B by atranscription lens 303B. A beam shape and a position of the guide laserbeam L3L are measured by the two-dimensional sensor.

The data that has been measured by the beam profiler 304B is input tothe wave front correction controller 60. The wave front correctioncontroller 60 transmits a control signal to an actuator 305 that adjustsan angle of the reflecting mirror 302A to control an angle of thereflecting mirror 302A in such a manner that a position of the guidelaser beam that is measure by the beam profiler 304B is set to be astandard position. Moreover, the wave front correction controller 60transmits a control signal to the wave front correction part 34 tocontrol a curvature of a wave front of the guide laser beam in such amanner that a beam shape of the guide laser beam is set to be in apredetermined value.

In the present embodiment that is configured as described above, thebeam profilers 304A and 304B are disposed on a side in which a guidelaser is transmitted to the reflecting mirrors 302A and 302B (on a rearside of the reflecting mirror), whereby the sensor 36C can be compactlyconfigured. Moreover, by an optical system for a measurement as shown inFIG. 34, a feedback control for a wave front of the guide laser beam arecarried out and a wave front of the driver pulsed laser beam iscontrolled simultaneously, whereby a desired wave front and a desireddirection of the driver pulsed laser beam can be stabilized.

Embodiment 19

A nineteenth embodiment of the present invention will be described inthe following with reference to FIG. 35. In the present embodiment, anactual focused image of the driver pulsed laser beam in the EUV chamber10B is measured to control the wave front correction part 45.

An EUV light emission region 11 (2) of the EUV chamber 10B is providedwith a sensor 44A. The sensor 44A is configured to be provided with, forexample, a beam splitter 330, the transcription lenses 331 and 332, andan imaging part 333. The imaging part 333 is configured to be providedwith, for example, an element such as a normal semiconductor CCD (ChargeCoupled Device) that has a sensitivity to the guide laser beam. As aresult, the EUV light emission region 11 (2) can be formed at a lowerprice as compared with an infrared CCD and can be easily handledadvantageously.

The beam splitter 330 reflects a part of the driver pulsed laser beamthat is focused into a predetermined position toward the transcriptionlenses 331 and 332. The other part of the driver pulsed laser beam isabsorbed into a dumper 19 and is converted into a heat.

The wave front correction controller 60A transmits a control signal tothe wave front correction part 45 to control the wave front correctionpart 45 in such a manner that a shape and a position of the laser beamthat has been focused into the chamber 10B are set to be a predeterminedshape and a predetermined position.

It is not necessary to correct a wave front of the driver pulsed laserbeam by only the wave front correction part 45. A wave front of thedriver pulsed laser beam can also be corrected by adjusting a positionand an orientation of each of the mirrors 16 (1), 16 (2), 17, and 18 ina light focusing region 11 (1).

In the present embodiment that is configured as described above, a finallight focusing result of the guide laser beam is measured, and a wavefront of the driver pulsed laser beam having a beam almost equivalent tothat of the guide laser beam is controlled, whereby a light focusingcharacteristic can be stabilized with a high degree of accuracy.

Embodiment 20

A twentieth embodiment of the present invention will be described in thefollowing with reference to FIG. 36. In the present embodiment, aShack-Hartmann sensor is used as an optical sensor part 360A. TheShack-Hartmann sensor 360A is configured to be provided with, forexample, a microlens array 361 composed of a large number of microlensesand an imaging element 362 such as a normal semiconductor CCD that has asensitivity to the guide laser beam. A band-pass filter BPF that makes aguide laser beam to be transmitted is disposed on the incident side ofthe Shack-Hartmann sensor 360A.

The most part of the guide laser beam L3 is reflected by a reflectingmirror 310. The reflecting mirror 310 is configured to reflect thedriver pulsed laser beam at a high degree of reflection and to partiallyreflect the guide laser beam. A laser beam L3L that is slightlytransmitted to the reflecting mirror 310 is incident to the microlensarray 361 via the band-pass filter BPF. An image of a light focusingpoint of each microlens is measured by the imaging part 362. A wavefront of the laser beam can be measured by analyzing a position of alight focusing point of each microlens.

In the present embodiment that is configured as described above, adistortion of a wave front and an angle (a direction) for the guidelaser beam can be simultaneously measured. As substitute for themicrolens array, an array such as a pinhole array and a Fresnel lensarray can also be used.

Embodiment 21

A twenty-first embodiment of the present invention will be described inthe following with reference to FIG. 37. In the present embodiment, thecharacteristics of a laser beam is measured based on an interferencefringe that is obtained by a wedge substrate 363. An optical sensor part360B is configured to be provided with the wedge substrate 363 and anormal semiconductor CCD 364 that has a sensitivity to the guide laserbeam. A band-pass filter BPF that makes a guide laser beam to betransmitted is disposed on the incident side of the optical sensor part360B. The wedge substrate 363 makes a carbon dioxide laser to betransmitted.

The most part of the guide laser beam L3 is reflected by a reflectingmirror 310. A guide laser beam L3L that is slightly transmitted to thereflecting mirror 310 is incident to the wedge substrate 363, and isreflected on both of the surface and the rear face of the wedgesubstrate 363.

By superimposing the guide laser beams that have been reflected on bothof the surface and the rear face of the wedge substrate 363 at apredetermined angle, an interference fringe is generated. Aninterference fringe that is obtained by the wedge substrate 363 isdetected by a normal semiconductor CCD 364 that has a sensitivity to theguide laser beam. A variation of a curvature of a wave front of theguide laser beam can be detected based on a degree of a curve of aninterference fringe. Moreover, a direction of the guide laser beam canbe detected based on a direction of a flow of an interference fringe.

Embodiment 22

A twenty-second embodiment of the present invention will be described inthe following with reference to FIGS. 38 to 40. In the presentembodiment, an optical sensor part 360C is configured to be providedwith a cylindrical lens 367 of a cylindrical concave face, a cylindricallens 368 of a cylindrical concave face, and a quartering type lightreceiving element 369 in order to detect a wave front of the guide laserbeam L3L. The bus lines of the both cylindrical lenses are disposed insuch a manner that the bus lines are crossed at a right angle. Adefinition of a bus line will be described later.

As shown in FIG. 39, a light receiving face of the light receivingelement 369 is divided into four regions DA1 to DA4 in a rhomboidalshape. A vertical output of the light receiving faces DA1 and DA3 and ahorizontal output of the light receiving faces DA2 and DA4 that aredisposed in a pattern orthogonal with the light receiving faces DA1 andDA3 are compared with each other by an operational amplifier 369B to beoutput.

As shown in FIG. 40( a), in the case in which a guide laser beam of aconcave face wave is transmitted to the lenses 367 and 368, the guidelaser beam as a beam that is long in a vertical direction is incident tothe light receiving element 369. The light receiving element 369 outputsa positive voltage.

As shown in FIG. 40( c), in the case in which a guide laser beam of aconvex face wave is transmitted to the lenses 367 and 368, the guidelaser beam as a beam that is long in a horizontal direction is incidentto the light receiving element 369. The light receiving element 369outputs a negative voltage.

On the other hand, as shown in FIG. 40( b), in the case in which a guidelaser beam of a plane wave is transmitted to the lenses 367 and 368, theguide laser beam in a generally circular shape is incident to the lightreceiving element 369. An output of the light receiving element 369 is0. As substitute for the light receiving element 369, a two-dimensionalsensor can also be used.

Embodiment 23

A twenty-third embodiment of the present invention will be described inthe following with reference to FIGS. 41 to 43. For an optical sensorpart 360C in accordance with the present embodiment, two cylindricallenses 368 (1) and 368 (2) that have a focal distance of the equivalentlength are disposed on the optical axis of the guide laser beam in sucha manner that the bus lines of the cylindrical lenses are crossed at aright angle. The bus line of the cylindrical lens is a line thatconnects apexes of a concave face. Each of the two cylindrical lenses368 (1) and 368 (2) is configured as a cylindrical lens of a cylindricalconcave face.

A light receiving element is disposed at an intermediate position D of afocal distance F1 of the cylindrical lens 368 (1) and a focal distanceF2 of the cylindrical lens 368 (2). As light receiving element, anelement such as a quartering type light receiving element shown in FIG.40 and a two-dimensional imaging element can be used. A position D onwhich a light receiving element is disposed is referred to as a sensorposition D in the following.

FIG. 41( a) shows a light focusing state of a guide laser beam viewed ina horizontal direction (X) and in a vertical direction (Y) in the casein which a guide laser beam of a plane wave is transmitted to the twocylindrical lenses 368 (1) and 368 (2).

The upper side of FIG. 41( a) shows a state of a guide laser beam in thecase in which the bus line of the first cylindrical lens 368 (1) isperpendicular to a horizontal direction (X) and the bus line of thesecond cylindrical lens 368 (2) is parallel to a horizontal direction(X). In this case, to an X direction, the first cylindrical lens 368 (1)functions as a convex lens, and the second cylindrical lens 368 (2)functions as a window.

Consequently, the guide laser beam is focused into a focus position F1of the cylindrical lens 368 (1) in a linear shape parallel to adirection that is crossed perpendicularly to the X direction, andspreads as a diverging light. The guide laser beam spreads to a certainlength L1 parallel to the X axis at a sensor position D shown by thedotted line.

The lower side of FIG. 41( a) shows a state of a guide laser beam in thecase in which the bus line of the first cylindrical lens 368 (1) isparallel to a vertical direction (Y) and the bus line of the secondcylindrical lens 368 (2) is perpendicular to a vertical direction (Y).In this case, to a Y direction, the first cylindrical lens 368 (1)functions as a window, and the second cylindrical lens 368 (2) functionsas a convex lens.

Consequently, the guide laser beam is focused into a focus position F2of the cylindrical lens 368 (2) in a linear shape parallel to adirection that is crossed perpendicularly to the Y direction. Since asensor position D is on a front side of the focus position F2, the guidelaser beam that has a certain length L2 parallel to the Y axis isdetected.

FIG. 41( b) shows a shape IM1 on an XY plane for the guide laser beamthat is measured at the sensor position D. A cross sectional shape IM1on an XY plane for the guide laser beam is a generally rectangular shapethat is provided with a width L1 in an X direction and a width L2 in a Ydirection. In the case in which F1 is set to be equivalent to F2 and thesensor position D is disposed at the center of a focal distance of eachof the cylindrical lenses 368 (1) and 368 (2), the cross sectional shapeIM1 is a square shape of L1=L2.

FIG. 42 shows a light focusing state of a guide laser beam in the casein which a guide laser beam of a convex face wave is transmitted to thetwo cylindrical lenses 368 (1) and 368 (2). The upper side of FIG. 42(a) is corresponded to the upper side of FIG. 41( a). The lower side ofFIG. 42( a) is corresponded to the lower side of FIG. 41( a). FIG. 43 isalso corresponded to FIG. 41 similarly.

As shown in the upper side of FIG. 42( a), the guide laser beam of aconvex face wave is focused into a position slightly far from a focusposition F1 of the cylindrical lens 368 (1) (on the right side in FIG.42) in a linear shape parallel to a direction that is crossedperpendicularly to the X direction. After that, the guide laser beamspreads as a diverging light. The guide laser beam spreads to a certainlength L1 a parallel to the X axis at a sensor position D.

As shown in the lower side of FIG. 42( a), the guide laser beam of aconvex face wave is focused into a position far from a focus position F2of the cylindrical lens 368 (2) in a linear shape parallel to adirection that is crossed perpendicularly to the Y direction. Since asensor position D is on a front side of the light focusing point, theguide laser beam has a certain length L2 a parallel to the Y axis.

FIG. 42( b) shows a shape IM2 on an XY plane for the guide laser beam ofa convex face wave. The shape IM2 of the guide laser beam is providedwith a width L1 a in an X direction and a width L2 a in a Y direction,and is a rectangular shape that is longer in a Y direction.

FIG. 43 shows a light focusing state of a guide laser beam in the casein which a guide laser beam of a concave face wave is transmitted toeach of the two cylindrical lenses 368 (1) and 368 (2). As shown in theupper side of FIG. 43( a), the guide laser beam is focused into aposition on a front side of a focus position F1 of the cylindrical lens368 (1) in a linear shape parallel to a direction that is crossedperpendicularly to the X direction. After the light focusing, the guidelaser beam spreads as a diverging light. The guide laser beam has acertain length L1 b parallel to the X axis at a sensor position D.

As shown in the lower side of FIG. 43( a), the guide laser beam isfocused into a position on a front side of a focus position F2 of thecylindrical lens 368 (2) in a linear shape parallel to a direction thatis crossed perpendicularly to the Y direction. Since a sensor position Dis on a front side of the light focusing point, the guide laser beam hasa certain length L2 b parallel to the Y axis.

FIG. 43( b) shows a shape IM3 on an XY plane for the guide laser beam ofa concave face wave. The shape IM3 of the guide laser beam is providedwith a width L1 b in an X direction and a width L2 b in a Y direction,and is a rectangular shape that is longer in an X direction.

Embodiment 24

A twenty-fourth embodiment of the present invention will be described inthe following with reference to FIG. 44. In the present embodiment, aconfiguration of a pre-pulse laser and a configuration that corrects anoptical characteristic of a pre-pulse laser are added to theconfiguration shown in FIG. 1. In the case in which a droplet DP reachesa predetermined position, the droplet DP is irradiated with a pre-pulsedlaser beam L4. By this configuration, a target material is expanded.Consequently, a density of a target material can be reduced to be asuitable value at the predetermined position which is irradiated with adriver pulsed laser beam L1, and a generation efficiency of an EUV lightcan be improved.

Consequently, the present embodiment is configured to be provided with apre-pulsed laser device 90 and an off-axis parabolic convex mirror 92that transmits a pre-pulsed laser beam to the chamber 10 via a window 13(2). As a pre-pulsed laser beam, a fundamental wave, a double harmonic,a triple harmonic, and a quadruple harmonic for a YAG laser can be usedfor instance. Alternatively, a fundamental wave or a harmonic light of atitanium sapphire laser of a pulse oscillation can also be use as apre-pulsed laser beam. In the present embodiment, although a targetmaterial supply unit that supplies a droplet DP is not shown, a dropletDP is supplied to a position of a light focusing point of a pre-pulsedlaser beam on an axis perpendicular to a plane of the paper forinstance.

A diameter of a tin droplet DP is 100 μm or less. Consequently, in orderto directly hit the droplet DP with a pre-pulsed laser beam, it isnecessary to manage a beam shape and a light focusing position with ahigh degree of accuracy. For the purpose, the present embodiment isconfigured to be provided with a mechanism that automatically correctsan optical performance of the pre-pulsed laser beam L4.

A guide laser beam introduction mirror (a guide laser beam introductionpart) 91 that introduces a guide laser beam L5 is disposed between thepre-pulsed laser device 90 and the off-axis parabolic convex mirror 92.A wave front correction part 95 is disposed on a downstream side of theguide laser beam introduction mirror 91. A sensor 96 is disposed betweenthe off-axis parabolic convex mirror 92 and the window 13 (2).

The guide laser beam L5 that is output from a guide laser device 93 isincident to the guide laser beam introduction mirror 91 via a lasercollimator 94, and is reflected by the guide laser beam introductionmirror 91.

The guide laser beam L5 is then incident to the off-axis parabolicconvex mirror 92 via the wave front correction part 95, and is reflectedtoward the window 13 (2). The sensor 96 detects an optical performanceof the guide laser beam L5 that travels to the chamber 10, and outputsthe optical performance to a wave front correction controller 97. Thewave front correction controller 97 controls the wave front correctionpart 95 in such a manner that the optical performance of the guide laserbeam L5 is in a predetermined value.

Moreover, the present embodiment is configured to be provided with aguide laser beam focusing point measuring instrument 400 that directlymeasures a shape and a position of a light focusing point of the guidelaser beam L5 on the chamber body 11 for an example. The measuringinstrument 400 is positioned at the end of the optical axes of thepre-pulsed laser beam L4 and the guide laser beam L5, and is disposed onthe chamber body 11.

The guide beam focusing point measuring instrument 400 is configured tobe provided with a band-pass filter (BSF) that makes only the guidelaser beam L5 to be transmitted, a transcription lens 401 that carriesout a transcription and an image formation of a light focusing point,and a CCD 402 that has a sensitivity to the guide laser beam L5 fordetecting a transcription image.

The guide laser beam is focused into a plasma luminous point PLZ, andthen spreads to be incident to the BSF. The BSF makes only the guidelaser beam to be transmitted. The guide laser beam is transmitted to thetranscription lens 401, and is incident to the CCD 402. The CCD 402detects a light focusing point image of the guide laser beam. The wavefront correction controller 97 controls the wave front correction part95 based on a shape and a position of a light focusing point of theguide laser beam that has been detected. By this configuration, a shapeand a position of a light focusing point of the pre-pulsed laser beamcan be stabilized with a high degree of accuracy.

In the present embodiment that is configured as described above, thecharacteristics of a light path through which the pre-pulsed laser beampasses can be modified on a steady basis by using the guide laser beamL5 that is output in an asynchronous manner with the pre-pulsed laserbeam L4. Consequently, a light focusing position and an output power ofthe pre-pulsed laser beam can be stabilized, whereby a droplet DP can bedirectly hit with the pre-pulsed laser beam stably and can be expanded.

Embodiment 25

A twenty-fifth embodiment of the present invention will be described inthe following with reference to FIGS. 45 to 49. In the presentembodiment described in the following (except for a twenty-ninthembodiment shown in FIG. 53), a pre-pulsed laser beam that is used forexpanding a target material in advance is used as a guide laser beam. Anextreme ultraviolet light source device 1A shown in FIG. 45 is common ina number of respects with the extreme ultraviolet light source device 1shown in FIG. 1. Although a guide laser beam of a continuous light or apseudo continuous light is used in the example shown in FIG. 1, apre-pulsed laser beam is also used as a guide laser beam in each of thefollowing embodiments that include the present embodiment. Morespecifically, a pre-pulsed laser beam has two functions composed of afunction as a guide laser beam for correcting an optical performance anda function for heating and expanding a droplet DP.

The extreme ultraviolet light source device 1A shown in FIG. 45 isconfigured to be provided with a pre-pulsed laser device 90 assubstitute for the guide laser device 50 shown in FIG. 1. A pre-pulsedlaser beam L4 that has been output from the pre-pulsed laser device 90is introduced to an inlet side of a main amplifier 35 (an upstream sidein a direction of travel of the laser beam) via a laser collimator 51.The pre-pulsed laser beam is incident to a chamber 10 via a lightfocusing system 40. As described later in FIG. 47, the pre-pulsed laserbeam L4 and the driver pulsed laser beam L1 are multiplexed in such amanner that the both beams have the same axis.

The guide laser beam introduction mirror 52 is configured as a beamsplitter by forming a thin coating that makes a driver pulsed laser beamto be transmitted and that makes a pre-pulsed laser beam to be reflectedat a relatively high degree of reflection on a diamond substrate. Sincea diamond has a high coefficient of thermal conductivity, an occurrenceof a distribution of temperature can be suppressed. As a result, even inthe case in which a laser beam is transmitted or reflected, a distortionof a wave front of a laser beam can be suppressed.

In the case in which a droplet DP is irradiated with the pre-pulsedlaser beam L4, the droplet DP is expanded due to a heat, and a densityof the droplet DP is reduced. A state in which the droplet DP isexpanded to reduce a density of the droplet DP is referred to as anexpanded state EXP in the embodiment.

FIG. 46 shows a state in which a droplet DP is irradiated with thepre-pulsed laser beam L4 to prepare an expanded state EXP and then thedriver pulsed laser beam L1 is irradiated. In the case in which tinhaving a suitable density in an expanded state EXP is irradiated withthe driver pulsed laser beam L1, tin becomes in a plasma state PLZ. Bythis configuration, an EUV light L2 is generated, and is supplied to theEUV exposure device 5.

FIG. 47 is a schematic explanatory diagram showing a relationship amonga driver pulsed laser beam L1, a pre-pulsed laser beam L4, and a dropletDP. As shown in FIG. 47( a), the pre-pulsed laser beam L4 and the driverpulsed laser beam L1 are set in such a manner that the both beams havethe same axis. A beam diameter of the pre-pulsed laser beam L4 is set tobe slightly larger than a diameter of a droplet DP. Since a wavelengthof the driver pulsed laser beam L1 is larger than that of the pre-pulsedlaser beam L4, a beam diameter of the driver pulsed laser beam L1 islarger than that of the pre-pulsed laser beam L4 to a satisfactoryextent. While a droplet DP moves along an axis Z1 in the chamber 10, thedroplet DP is irradiated with the pre-pulsed laser beam L4.

FIG. 47( b) shows a state immediately after the droplet DP is irradiatedwith the pre-pulsed laser beam L4. In the case in which the droplet DPis irradiated with the pre-pulsed laser beam L4, a part of the dropletDP is separated from the droplet DP and is dispersed in all directionsdue to the impact to be a dispersed material De and a pre-plasma statePre. It is supposed that the pre-plasma state Pre is a mixed state of ametal vapor and plasma. In the case in which the droplet DP isirradiated with the pre-pulsed laser beam L4, the droplet DP is expandeddue to a heat, and becomes in an expanded state EXP. The expanded stateEXP is adjusted to be a value in such a manner that a generationefficiency of an EUV light is increased.

FIG. 47( c) shows a state in which a target material (Sn) in an expandedstate EXP is irradiated with a driver pulsed laser beam L1. A beamdiameter of the driver pulsed laser beam L1 is large to a satisfactoryextent as described above, a target material in a pre-plasma state Preand a target material De that has been dispersed in all directions areirradiated with a driver pulsed laser beam L1, and become in a plasmastate PLZ.

FIG. 48 is a flowchart of a processing for carrying out a wave frontcorrection. The present processing is carried out by the wave frontcorrection controller 60. The processing shown in FIG. 48 is providedwith the steps S11 to S14 that are common with the processing shown inFIG. 3. The processing shown in FIG. 48 and the processing shown in FIG.3 are different from each other in the step S10A.

In the present embodiment, the wave front correction controller 60detects the pre-pulsed laser beam L4 by the sensor 44, and acquires ameasured value Da of the pre-pulsed laser beam L4 from the sensor 44(S10A). The subsequent steps are equivalent to those described in FIG.3, and the descriptions thereof are omitted.

FIG. 49 is a flowchart that shows an operation of a laser controller 70and an EUV light source controller 80. The flowchart shown in FIG. 49 isprovided with the steps S20 to S22 and S24 that are common with theflowchart described in FIG. 4. The different points are that the S23 inFIG. 4 is replaced by the S27 and that the S25 and S26 are added newly.

In the case in which the laser controller 70 receives an irradiation OKsignal from the wave front correction controller 60 (S20: YES), thelaser controller 70 notifies the EUV light source controller 80 of thatan adjustment of the driver pulse laser light source device 2 has beencompleted (S21). In the case in which the EUV light source controller 80receives an adjustment completion notice from the laser controller 70,the EUV light source controller 80 outputs a light emission command tothe laser controller 70.

The laser controller 70 stops an output of a driver pulsed laser beamand stands by until a light emission command is output from the EUVlight source controller 80 (S22: NO, S24). While an output of a driverpulsed laser beam is stopped, the pre-pulsed laser device 90 outputs apre-pulsed laser beam, and a correction of an optical system is carriedout by the processing described in FIG. 48 (S25).

In the S25, a pre-pulsed laser beam is output at a weak pulse energythat is specified in advance in such a manner that a physical change isnot applied to a droplet DP. The weak pulse energy is corresponded to a“first output”.

That a physical change is not applied to a droplet DP means that a shapeof a droplet DP is not changed from a state before a pre-pulsed laserbeam is irradiated to a state after a pre-pulsed laser beam isirradiated. More specifically, an output of a pre-pulsed laser beam isspecified to be weak in such a manner that a droplet DP is not expandeddue to a heat and that a part of the droplet DP is not dispersed forinstance after an irradiation of a pre-pulsed laser beam. In otherwords, a pre-pulsed laser beam having a low intensity by which anoptical performance can be corrected is output.

On the other hand, in the case in which the laser controller 70 receivesa light emission command from the EUV light source controller 80 (S22:YES), the laser controller 70 makes the pre-pulsed laser device 90 tooutput a pre-pulsed laser beam at a normal pulse energy as a “secondoutput” (S26). The normal pulse energy is an energy that can expand adroplet DP due to a heat to make the droplet DP to have a predetermineddensity.

The laser controller 70 makes the driver laser oscillator 20 to output adriver pulsed laser beam at a predetermined timing, and makes a targetmaterial in an expanded state to be irradiated with the driver pulsedlaser beam (S27). By this configuration, an EUV light is generated, andsupplied to the EUV exposure device 5.

The present embodiment that is configured as described above has anoperation effect equivalent to that of the first embodiment since apre-pulsed laser beam can be used as a guide laser beam whereby aperformance of an optical system can be adjusted. Moreover, in thepresent embodiment, a pre-pulsed laser beam that is used for improving ageneration efficiency of an EUV light can also be used as a guide laserbeam that is used for adjusting a performance of an optical system.Consequently, in the present embodiment, a reliability can be improvedwithout complicating the configuration.

Embodiment 26

A twenty-sixth embodiment of the present invention will be described inthe following with reference to FIG. 50. In the present embodiment, amodified example of the processing described in FIG. 49 will bedescribed. FIG. 50 is a flowchart that shows an operation of a lasercontroller 70 and an EUV light source controller 80. The flowchart shownin FIG. 50 is provided with the steps S20 to S24, S26, and S27 that arecommon with the flowchart described in FIG. 49. The different point isthat the S25 in FIG. 49 is replaced by the S25A. Consequently, thedifferent point will be described in the following.

In the present embodiment, in a period when an output of a driver pulsedlaser beam is stopped (S24), a pre-pulsed laser beam is output from thepre-pulsed laser device 90 at a timing when a droplet DP is not hit(S25A).

A droplet DP is supplied from a target material supply part 15 to thechamber 10 at a constant frequency. As well as in the period when adriver pulsed laser beam is output, even in the period when a driverpulsed laser beam is not output, a droplet DP is supplied from thetarget material supply part 15 at a constant frequency during anoperation of the extreme ultraviolet light source device 1.

The laser controller 70 outputs a pre-pulsed laser beam at apredetermined timing in such a manner that the pre-pulsed laser beampasses through a space between droplets DP. An optical performance of anoptical system is adjusted by using the pre-pulsed laser beam. Thepresent embodiment that is configured as described above has anoperation effect equivalent to that of the twenty-fifth embodiment.

Embodiment 27

A twenty-seventh embodiment of the present invention will be describedin the following with reference to FIG. 51. In the present embodiment, apre-pulsed laser beam L4 is introduced to the optical system and ismultiplexed with the driver pulsed laser beam L1 on a front side of themain amplifier 35 (1). As shown in the general block diagram of FIG. 51,a guide laser beam introduction mirror 52A is disposed between the lastpreamplifier 32 (4) of a plurality of preamplifiers 32 and the firstmain amplifier 35 (1) of a plurality of main amplifiers 35.

The guide laser beam introduction mirror 52A is configured as a beamsplitter by forming a thin coating on a diamond substrate for instance.A thin coating that makes a pre-pulsed laser beam to be transmitted andthat makes a driver pulsed laser beam to be reflected at a relativelyhigh degree of reflection is formed on the guide laser beam introductionmirror 52A. The present embodiment that is configured as described abovehas an operation effect equivalent to that of the twenty-fifthembodiment.

Embodiment 28

A twenty-eighth embodiment of the present invention will be described inthe following with reference to FIG. 52. The present embodiment isapplied to the case in which a laser focusing system (a laser focusingoptical system) that focuses a laser beam into a predetermined point isdisposed in the chamber 10A or close to the chamber 10A. In the case inwhich a laser focusing system 500 is disposed in the chamber 10A orclose to the chamber 10A, each optical component that configures thelaser focusing system 500 is greatly affected by a heat. This is becausea heat from not only a driver pulsed laser beam but also the chamber 10Ais applied to the laser focusing system 500. Consequently, the presentembodiment maintains an optical performance of the laser focusing system500 that is easy to be affected by a heat as described in the following.

The chamber 10A is configured to be provided with, for example, a lightfocusing region 11 (1) that arranges a driver pulsed laser beam that isincident from the driver pulse laser light source device 2 and an EUVlight emission region 11 (2) that generates an EUV light by irradiatinga droplet DP with a driver pulsed laser beam. As described in FIG. 8,the two regions 11 (1) and 11 (2) are partitioned by a wall. The lightfocusing region 11 (1) and the EUV light emission region 11 (2) arecommunicated with each other via a small hole that has been formed inthe partition wall that partitions the regions 11 (1) and 11 (2).

The light focusing region 11 (1) is provided with the laser focusingsystem 500 that is configured to be provided with a plurality of opticalelements. The laser focusing system 500 is configured by disposing, forexample, the off-axis parabolic convex mirrors 16 (1) and 16 (2), areflecting mirror 17, and an off-axis parabolic concave mirror 18 at thepredetermined positions.

A driver pulsed laser beam L1 is reflected by a reflecting mirror (abeam splitter) 41(2)A, and is incident to the laser focusing system 500via a diamond window 13. The driver pulsed laser beam L1 is reflected bythe off-axis parabolic concave mirror 18, and is incident to theoff-axis parabolic convex mirror 16 (1). A beam diameter of the driverpulsed laser beam L1 is expanded by being reflected on the off-axisparabolic concave mirror 18 and the off-axis parabolic convex mirror 16(1).

In the third embodiment shown in FIG. 8, the purpose of the reflectingmirror 41(2) is to make a driver pulsed laser beam L1 to be reflected.However, the reflecting mirror 41(2)A in accordance with the presentembodiment is configured as a beam splitter that makes a driver pulsedlaser beam L1 to be reflected and that makes a pre-pulsed laser beam L4to be transmitted. The beam splitter 41(2)A is configured by forming athin coating on a diamond substrate for instance.

A driver pulsed laser beam L1 that is specified to have a predeterminedbeam diameter is incident to and reflected by a high reflection planemirror 17, and is incident to another off-axis parabolic convex mirror16 (2). The driver pulsed laser beam L1 that has been reflected by theoff-axis parabolic convex mirror 16 (2) is irradiated to a droplet DPvia a hole part 14A of the EUV light collector mirror 14.

A pre-pulsed laser beam L4 that has been output from the pre-pulsedlaser device 90 is incident to the beam splitter 41(2)A via another beamsplitter 503. The beam splitter 503 is configured by forming a coatingthat reflects a pre-pulsed laser beam L4 at a degree of reflection inthe range of 4% to 50% for instance on a diamond substrate.

The pre-pulsed laser beam L4 is incident to the laser focusing system500 via the beam splitter 41(2)A and the diamond window 13. Similarly tothe driver pulsed laser beam L1, the pre-pulsed laser beam L4 istransmitted to the laser focusing system 500, whereby a beam diameter ofthe pre-pulsed laser beam L4 is adjusted. The pre-pulsed laser beam L4is then irradiated to a droplet DP.

A part of the pre-pulsed laser beam L4 that has been irradiated to adroplet DP is reflected on the surface of the droplet DP, and returns ona light path that has been used when the pre-pulsed laser beam L4 wasincident to the droplet DP. A laser beam that is reflected by thedroplet DP to be returned is referred to as a return light in theembodiments.

A return light of the pre-pulsed laser beam L4 is incident to the beamsplitter 503 via the laser focusing system 500 and the beam splitter41(2)A. A part of the return light is reflected by the beam splitter503. The return light that has been reflected by the beam splitter 503passes through a light focusing lens 504, and is incident to a CCDsensor 505. By this configuration, an image formation of a transcriptionimage of a droplet DP is carried out in the CCD sensor 505.

A laser focusing system controller 502 controls the laser focusingsystem 500 by outputting a control signal to a laser focusing systemactuator 501 based on a transcription image of a droplet DP that isdetected by the CCD sensor 505. The laser focusing system actuator 501is a device that adjusts a position and/or an orientation of each of theoptical components 16 (1), 16 (2), 17, and 18 that are disposed in thelaser focusing system 500.

For instance, the laser focusing system controller 502 controls anoptical axis of the laser focusing system 500 in such a manner that aposition and/or a size of a transcription image of a droplet DP become atarget position and/or a target size. Moreover for instance, the laserfocusing system controller 502 controls a focus position of the laserfocusing system 500 in such a manner that a size of a transcriptionimage of a droplet DP becomes a minimum size.

The present embodiment that is configured as described above has anoperation effect equivalent to that of the twenty-fifth embodiment.Moreover, in present embodiment, an optical performance of the laserfocusing system 500 that is affected by a heat from not only a driverpulsed laser beam L1 but also the chamber 10A can also be controlled byusing the pre-pulsed laser beam L4.

Embodiment 29

A twenty-ninth embodiment of the present invention will be described inthe following with reference to FIG. 53. The present embodiment iscorresponded to a modified example of the twenty-eighth embodimentdescribed in FIG. 52. In present embodiment, a visible light lamp 510and a collimate lens 511 are used as substitute for the pre-pulsed laserdevice 90. In present embodiment, an expansion of a droplet DP due to aheat with a pre-pulsed laser beam is not carried out.

A visible light that spreads as a diverging light from the visible lightlamp 510 passes through the collimate lens 511, and is converted into aparallel guide beam L4A. A part of the guide beam L4A is reflected by adroplet DP, and is incident to the CCD sensor 505.

Embodiment 30

A thirtieth embodiment of the present invention will be described in thefollowing with reference to FIG. 54. In present embodiment, a lightfocusing position P1 of a pre-pulsed laser beam and a light focusingposition P2 of a driver pulsed laser beam are different from each other.FIG. 54( a) shows a light focusing position P1 of a pre-pulsed laserbeam L4, and FIG. 54( b) shows a light focusing position P2 of a driverpulsed laser beam L1.

A light focusing position P2 of a driver pulsed laser beam L1 isspecified to be shifted from a light focusing position P1 of apre-pulsed laser beam L4 by a distance ΔL on a downstream side in adirection of travel of a laser beam. As shown in FIG. 54( b) forinstance, the light focusing position P2 can be shifted in the back fromthe light focusing position P1 by a distance ΔL by adjusting adivergence of the driver pulsed laser beam L1 that is incident to thebeam splitter 41(2)A in advance.

The present embodiment that is configured as described above has anoperation effect equivalent to that of the twenty-fifth embodiment.Moreover, in the present embodiment, a light focusing position P1 of apre-pulsed laser beam and a light focusing position P2 of a driverpulsed laser beam can be different from each other. A dispersing speedof a dispersed material De is high and a dispersed material De isdispersed in a wide range in some cases depending on an irradiationcondition of the pre-pulsed laser beam L4. In this case, in the presentembodiment, a dispersed material De that has been dispersed in a widerange and a target material in an expanded state can be irradiated witha driver pulsed laser beam in an effective manner, whereby a generationefficiency of an EUV light can be improved.

While the preferred embodiments in accordance with the present inventionhave been described above, the present invention is not limited to theembodiments described above. Those skilled in the art can carry outvarious changes, modifications, and functional additions withoutdeparting from the scope of the present invention. Moreover, the scopeof the present invention includes a configuration in which theembodiments described above are combined properly as needed.

For instance, in the embodiment in which a guide laser beam isintroduced to an optical system of a pre-pulsed laser beam, a guidelaser beam is also introduced to an optical system of a driver pulsedlaser beam. However, the present invention is not limited to theembodiment, and a configuration in which only the characteristics of anoptical system of a pre-pulsed laser beam is corrected can also beadopted. More specifically, the configurations (50, 51, and 52) for aguide laser beam corresponded to a driver pulsed laser beam can also beremoved.

Moreover, in the case in which a correction of a chromatic aberration isenabled according to a relationship between a wavelength of a pre-pulsedlaser beam and a wavelength of a guide laser beam, an optical systemwhich a pre-pulsed laser beam and a guide laser beam that iscorresponded to the pre-pulsed laser beam pass through can be configuredby an optical system of a refracting type. Furthermore, a pre-pulsedlaser device can be configured to be provided with an oscillator thatoscillates a pre-pulsed laser beam and at least one amplifier thatamplifies a pre-pulse laser or an amplified laser.

Moreover, while a laser device that is used for an extreme ultravioletlight source device has been described above as an example, the presentinvention is not limited to the example. For instance, a laser devicecan also be used for other applications such as a laser processing.

EXPLANATION OF REFERENCE

-   1: Extreme ultraviolet light source device-   2: Driver pulse laser light source device-   5: EUV exposure device-   10, 10A, 10B: Chambers-   11: Chamber body-   11 (1): Light focusing region-   11 (2): EUV light emission region-   12: Connection part-   13: Window-   14: EUV light collector mirror-   14A: Hole part-   15: Target material supply part-   16: Off-axis parabolic concave mirror-   17: Reflecting mirror-   18: Mirror-   19: Dumper-   20: Driver laser oscillator-   21: Laser chamber-   22: Rear mirror-   23: Plane output mirror-   30: Amplification system-   31: Relay optical system-   32: Preamplifier-   33: Saturable absorber-   34, 34A, 34B, 34C, 34D: Wave front correction parts-   35: Main amplifier-   36, 36A, 36B, 36C: Sensors-   37: Spatial filter-   38: Reflecting mirror-   40: Light focusing system-   41: Reflecting mirror-   41(2)A: Beam splitter-   42: Off-axis parabolic concave mirror-   43: Relay optical system-   44, 44A: Sensors-   45: Wave front correction part-   46: Isolator-   50: Guide laser device-   51: Laser collimator-   52, 52A: Guide laser beam introduction mirrors-   60, 60A: Wave front correction controller-   70: Laser controller-   80: EUV light source controller-   90: Pre-pulsed laser device-   91: Guide laser beam introduction mirror-   92: Off-axis parabolic convex mirror-   93: Guide laser device for a pre-pulsed laser beam-   94: laser collimator-   95: Wave front correction part-   96: Sensor-   97: Wave front correction controller-   100, 100A: Angle correction parts-   110: VRWM-   111: Reflecting mirror-   200, 200A, 200B, 200C, 200D, 200E, 200F: Wave front curvature    correction parts-   300: Reflecting mirror-   301: Diffraction type mirror-   360, 360A, 360B, 360C, 360D: Optical sensor parts-   400: Guide laser beam focusing point measuring instrument-   401: Transcription lens-   402: CCD-   500: Laser focusing system-   501: Laser focusing system actuator-   502: Laser focusing controller-   503: Beam splitter-   504: Light focusing lens-   505: CCD sensor-   L1: Driver pulsed laser beam-   L2: EUV light-   L3: Guide laser beam-   L4: Pre-pulsed laser beam-   L5: Guide laser beam for a pre-pulsed laser beam

The invention claimed is:
 1. An extreme ultraviolet light sourceapparatus that generates an extreme ultraviolet light by irradiating atarget material with a driver pulsed laser beam for turning the targetmaterial into plasma, comprising: a chamber; a prepulse laser deviceconfigured for outputting a prepulse laser beam; a prepulse guide laserdevice configured for outputting a prepulse guide laser beam; a firstdelivering mirror configured for synchronizing traveling directions ofthe prepulse laser beam and the prepulse guide laser beam; a driverpulsed laser device configured for outputting the driver pulsed laserbeam; a driver pulsed guide laser device configured for outputting adriver pulsed guide laser beam; a second delivering mirror configuredfor synchronizing traveling directions of the driver pulsed laser beamand the driver pulsed guide laser beam; a mirror configured forreflecting the prepulse laser beam passing through the first deliveringmirror and transmitting the driver pulsed laser beam passing through thesecond delivering mirror; a focusing system configured for guiding theprepulse laser beam reflected by the mirror and the driver pulsed laserbeam passing through the mirror to the target material; a firstcorrection part located between the first delivering mirror and thefocusing system, including a first optical element where the prepulselaser beam enters, and configured for rotating, moving or transformingthe first optical element; a second correction part located between thesecond delivering mirror and the focusing system, including a secondoptical element where the driver pulsed laser beam enters, andconfigured for rotating, moving or transforming the second opticalelement; a sensor located between the mirror and the chamber; and acontroller configured for controlling at least one of the firstcorrection part and the second correction part based on a detectionresult of the sensor.
 2. The apparatus according to claim 1, wherein thesensor includes one of a beam profiler, a calorimeter or a pyroeletricsensor as being a power sensor, and a wave front sensor.
 3. Theapparatus according to claim 1, wherein the mirror include a diamondsubstrate.
 4. The apparatus according to claim 1, wherein at least oneof the first delivering mirror and the second delivering mirror includesa diamond substrate.
 5. An extreme ultraviolet light source apparatusthat generates an extreme ultraviolet light by irradiating a targetmaterial with a driver pulsed laser beam for turning the target materialinto plasma, comprising: a prepulse laser device configured foroutputting a prepulse laser beam; a prepulse guide laser deviceconfigured for outputting a prepulse guide laser beam; a deliveringmirror configured for synchronizing traveling directions of the prepulselaser beam and the prepulse guide laser beam; a driver pulsed laserdevice configured for outputting the driver pulsed laser beam; a mirrorconfigured for reflecting the prepulse laser beam passing through thedelivering mirror and transmitting the driver pulsed laser beam; afocusing system configured for guiding the prepulse laser beam reflectedby the mirror and the driver pulsed laser beam passing through themirror to the target material; a correction part located between thedelivering mirror and the focusing system, including a first opticalelement where the prepulse laser beam enters, and configured forrotating, moving or transforming the first optical element; a sensorconfigured for detecting at least one of the prepulse laser beam and theprepulse guide laser beam; and a controller configured for controllingthe correction part based on a detection result of the sensor.
 6. Theapparatus according to claim 5, wherein the sensor includes one of abeam profiler, a calorimeter or a pyroeletric sensor as being a powersensor, and a wave front sensor.
 7. The apparatus according to claim 5,wherein the mirror include a diamond substrate.
 8. An extremeultraviolet light source apparatus that generates an extreme ultravioletlight by irradiating a target material with a driver pulsed laser beamfor turning the target material into plasma, comprising: a chamber; aprepulse laser device configured for outputting a prepulse laser beam; aprepulse guide laser device configured for outputting a prepulse guidelaser beam; a first delivering mirror configured for synchronizingtraveling directions of the prepulse laser beam and the prepulse guidelaser beam; a driver pulsed laser device configured for outputting thedriver pulsed laser beam; a driver pulsed guide laser device configuredfor outputting a driver pulsed guide laser beam; a second deliveringmirror configured for synchronizing traveling directions of the driverpulsed laser beam and the driver pulsed guide laser beam; a mirrorconfigured for transmitting the prepulse laser beam passing through thefirst delivering mirror and reflecting the driver pulsed laser beampassing through the second delivering mirror; a focusing systemconfigured for guiding the prepulse laser beam passing through themirror and the driver pulsed laser beam reflected by the mirror to thetarget material; a first correction part located between the firstdelivering mirror and the focusing system, including a first opticalelement where the prepulse laser beam enters, and configured forrotating, moving or transforming the first optical element; a secondcorrection part located between the second delivering mirror and thefocusing system, including a second optical element where the driverpulsed laser beam enters, and configured for rotating, moving ortransforming the second optical element; a sensor located between themirror and the chamber; and a controller configured for controlling atleast one of the first correction part and the second correction partbased on a detection result of the sensor.
 9. The apparatus according toclaim 8, wherein the sensor includes one of a beam profiler, acalorimeter or a pyroeletric sensor as being a power sensor, and a wavefront sensor.
 10. The apparatus according to claim 8, wherein the mirrorinclude a diamond substrate.
 11. The apparatus according to claim 8,wherein at least one of the first delivering mirror and the seconddelivering mirror includes a diamond substrate.